Petty bloke hiding key (4)
I believe the answer is:
mean
'petty' is the definition.
(thesaurus)
'bloke hiding key' is the wordplay.
'bloke' becomes 'man' (I've seen this in other clues**).
'hiding' means one lot of letters goes inside another.
'key' becomes 'e' (I've seen this in other clues).
'man' enclosing 'e' is 'MEAN'.
(Other definitions for mean that I've seen before include "Common" , "Bad-tempered" , "Parsimonious" , "Base; tight" , "Petty" .)