The teenager told Press Association Sport: " It was awesome. The whole week's been great. Obviously not the result we wanted but all the guys are really nice and we get on really well so it's been a great experience.
"I don't really get to see this level of tennis at court level so even just to be here and watch all the little things they do is great."
British tennis is all too familiar with the tale of players who excel at junior level then struggle to make the transition into the senior game but Clarke is shaping up to be the opposite, and from a generation that had been criticised for a dearth of talent.
Clarke has consistently been the best of the bunch, and he was affected by the Lawn Tennis Association's dramatic slashing of high-performance funding in recent years.
Travelling to the biggest tournaments was difficult for a player from inner city Derby without a wealthy family behind him.
He kept costs down by being coached by his brother Curtis and sister Yasmin, both of whom have also played on the professional circuit and remain a big part of his team.
"My sister started playing the week I was born," said Clarke. "As soon as I could walk it's all I've ever known because we lived really close to a tennis club so I used to stay there for hours and just hit balls with my brother and sister and my dad.
"Obviously your family want the best for you over anyone else. You can always trust what they say. They've always coached me and I listen to them a lot.
"It's a really good relationship. Sometimes we have arguments but it's forgotten as soon as we leave the court."
The Futures Tour, the lowest level of the professional game, is a notoriously difficult place for young players to thrive but Clarke has improved rapidly.
After winning back-to-back tournaments in Egypt last November he won another in Turkey last month, earning the call from Smith.
At 418 in the world, Clarke is the only British teenager ranked in the top 800, while only eight players younger than him sit above him worldwide.
He said: "I always worked really hard. My game was a bit lost at juniors but there were a lot of things I was working on, trying to play a bigger game, which I wasn't that comfortable with.
"My last year of juniors wasn't great, I had a few things off court as well, but when I got everything sorted my tennis started improving and I'm just really happy how quickly I've gone up the rankings."
The LTA has supported him through non-direct funding, with the latest reward being the services of Spanish coach Esteban Carril, who masterminded Johanna Konta's spectacular rise before they split at the end of last season.
"He's a really good addition to my team," said Clarke.
"Because my sister and my brother have never gone past Futures or Challenger level and he's coached Jo and (Roberto) Bautista Agut, there's a lot of things at the top of the game that we would have never seen. He's had a really big impact in the time so far."
Clarke is a long way from taking on childhood idol Nadal - "I didn't really know how tough it was to play like him. I tried for a long time but it didn't work for me" - just yet.
But he will try his hand at the second-tier Challenger Tour in Korea for the first time next month and could well find grass-court wild cards, including Wimbledon, coming his way this summer.
He has set himself the target of a top-200 ranking by the end of the year, with the aim of halving it every year after that.
If he sticks to his path, Clarke's Davis Cup experience in Rouen will not be his last.