Winner hard to be found in group (5)
I believe the answer is:
champ
'winner' is the definition.
(thesaurus)
'hard to be found in group' is the wordplay.
'hard' becomes 'h'.
'to be found in' indicates putting letters inside.
'group' becomes 'camp' (camp is a kind of group**).
'h' inserted within 'camp' is 'CHAMP'.
(Other definitions for champ that I've seen before include "Munch (at the bit?)" , "boxer who is top dog?" , "Supreme competitor" , "Crush" , "Mashed potato with scallions" .)