He's ardent, I fancy, revealing crush (10)
I believe the answer is:
dishearten
'crush' is the definition.
'he's ardent i fancy' is the wordplay.
'fancy' indicates anagramming the letters.
'hes'+'ardent'+'i'='hesardenti'
'hesardenti' is an anagram of 'DISHEARTEN'.
'revealing' acts as a link.
(Other definitions for dishearten that I've seen before include "Take away bottle" , "Take hope from" , "Cause (someone) to lose confidence" , "Put a damper on" , "Bring down" .)