Rude greengrocer holding university qualification (6)
I believe the answer is:
degree
'university qualification' is the definition.
(I've seen this before)
'rude greengrocer holding' is the wordplay.
'holding' says the answer is hidden in the clue.
'DEGREE' can be found hidden inside 'rude greengrocer'.
(Other definitions for degree that I've seen before include "Angular unit and college award" , "Position on a scale" , "small part" , "It's given to college graduates" , "Academic award - 60 minutes" .)