Hairy armpit hunt is successful (10)
I believe the answer is:
triumphant
'successful' is the definition.
(I've seen this in another clue)
'hairy armpit hunt' is the wordplay.
'hairy' indicates an anagram (hairy can mean difficult or tricky).
'armpit'+'hunt'='armpithunt'
'armpithunt' anagrammed gives 'TRIUMPHANT'.
'is' is the link.
(Other definitions for triumphant that I've seen before include "Victor may be" , "Jubilantly victorious" , "successful" .)