Despite Clare's first-half treble and a try from Rangi Chase on his Castleford farewell, the visitors were four points down at the break as Tigers-bound Frankie Mariano (twice), Kay and Kyle Trout went in for the home side.
Wakefield extended their lead after the break when Kay raced away for his second, but Weller Hauraki crashed over to reduce the gap to two before Clare scored his fourth.
Ali Lauitiiti then levelled it at 32-32 before charging down Chase's kick for glory and sending Kay away for a brilliant finish.
It was perhaps harsh on Cas, who had taken the lead when Clare stripped the Wildcats' defence to race the length of the field and score.
Then, after an error from Peter Fox, they extended their lead, with Chase displaying the footwork his side will miss as he danced in, with Kirk Dixon converting from wide out for a 10-0 lead.
Wakefield's response was immediate, with Paul Aiton sending Matty Wildie through and he picked out the supporting Mariano.
Ben Cockayne tagged a goal but Castleford were soon in again as another Fox lapse allowed Chase to put Clare in.
But Wakefield continued the see-saw nature of the game as first Kay from close range and then Mariano from a similar distance saw them take the lead.
Cockayne and Hauraki then spent 10 minutes on the sidelines for a bust-up, before smart work from Jordan Tansey sent Clare in for a third time.
Richard Mathers' classy play would put Trout in, though, and when Kay cashed in some neat work from Cockayne, Lauitiiti and Mariano, Wakefield were coasting.
Lee Smith coughed the ball up, however, and Hauraki went in, before Clare's fourth gave his side the lead when he took a Tansey pass, went inside and then chased down his own kick ahead.
Dixon's goal made it 32-28 and Ben Reynolds would have added to that were it not for a crunching hit from Justin Poore.
On the back of that, Lauitiiti squared things up but Smith missed the kick, meaning everything was on the line.
And then, on his last play for Castleford, Chase tried a creative kick ahead which Lauitiiti shovelled up before giving to Kay who brought the house down.