A copper with little enthusiasm (8)
I believe the answer is:
appetite
'enthusiasm' is the definition.
(thesaurus)
'a copper with little' is the wordplay.
'copper' becomes 'p'.
'with' is a charade indicator (letters next to each other).
'little' becomes 'petite' ('petite' can be similar in meaning to 'little'**).
'a'+'p'+'petite'='APPETITE'
(Other definitions for appetite that I've seen before include "Natural craving" , "stomach" , "Justification for dining" , "'Strong desire, craving (8)'" , "A feeling of craving something" .)