The second-row weaved in from around 40m, beating a raft of defenders, on his home debut for the club in Friday’s 32-16 win.
Clarkson, of course, was released by Rovers at the end of last season and spent more than three months looking for a new club before Castleford gave him a chance in January.
The decision has paid dividends for both the club and player. Amid a raft of injuries to their second-rows he debuted in the win at London Broncos and followed up with a man-of-the-match display against Rovers.
On his 40m effort – a first for Castleford – Clarkson admitted: “It doesn’t get much better.
“It was a good feeling and a good try, especially to score it at the Wheldon Road end and against my old team Hull KR.
“I don’t think I’ve ever scored a better one, to be fair.
“It does add a little bit beforehand (facing a former club) but I tried taking all the emotion out of it as it can end up affecting your performance.
“I just wanted to play my normal game and thankfully I managed to do that and help us get the win.
“I didn’t think I’d score it from where I was when I was running.
“I just put my foot down. I had Chris Atkin and Danny Addy after me, but I was just determined to get there.”
The former Leeds Rhinos forward, 28, also topped the tackle count with 36 and made five tackle busts.
He conceded playing in the last two games for the early Super League leaders has boosted him significantly.
Clarkson said: “It’s brought back a lot of confidence for me.
“Leaving Hull KR like I did, I did lose it a bit so it’s been good to get back out there and playing again.
“I know I’m good enough to do it, but it’s good to show it once more.”
He hopes to retain his place as Castleford head to Warrington Wolves on Thursday, opponents who lost for the first time this season when falling 23-22 against Catalans Dragons at the weekend.
“They’ll be wanting to bounce back after what happened in Perpignan, but we want to make it five from five and stay top of the league,” said Clarkson