Exceptional teenager winning man’s approval (9)
I believe the answer is:
agreement
'approval' is the definition.
(thesaurus)
'exceptional teenager winning man's' is the wordplay.
'exceptional' is an anagram indicator.
'winning' is an insertion indicator (some letters win or obtain others).
'man' becomes 'm'.
'teenager' is an anagram of 'agreeent'.
'agreeent' enclosing 'm' is 'AGREEMENT'.
(Other definitions for agreement that I've seen before include "match" , "consensus" , "deal" , "understanding" , "Correspondence" .)