He's in form to do well (5)
I believe the answer is:
shine
'do well' is the definition.
(I've seen this in another clue)
'he's in form' is the wordplay.
'form' indicates an anagram (a different form of the same letters).
'hes'+'in'='hesin'
'hesin' with letters rearranged gives 'SHINE'.
'to' acts as a link.
(Other definitions for shine that I've seen before include "Lustre" , "Glimmer" , "Gleam, glisten" , "Mislaying" , "Administrator for monarch who is a minor" .)