Not all educated gents may be sharp (4)
I believe the answer is:
edge
'sharp' is the definition.
(thesaurus)
'not all educated gents may' is the wordplay.
'not all' indicates a hidden word (only some of the letters).
'EDGE' is hidden in the letters of 'educated gents may'.
'be' is the link.
(Other definitions for edge that I've seen before include "Sharp ridge" , "Final line" , "Sharpened side of blade" , "Bite" , "marginal advantage" .)