Grape can't contain a nut (5)
I believe the answer is:
pecan
'a nut' is the definition.
(type of nut)
'grape can't contain' is the wordplay.
'contain' indicates the answer is hidden within the clue (words from the clue contain the answer).
'PECAN' can be found hidden inside 'grape cant'.
(Other definitions for pecan that I've seen before include "Nut of American hickory tree" , "Nutty type" , "Nut tree of the southern United States and Mexico" , "Smooth pinkish-brown nut, nice in pie" , "Walnut-like nut" .)