Most of the fruit or vegetable (3)
I believe the answer is:
pea
'vegetable' is the definition.
(I've seen this before)
'most of the fruit' is the wordplay.
'most of' means to remove the last letter.
'the fruit' becomes 'pear' (pear is a kind of fruit).
'pear' with its last letter taken off is 'PEA'.
'or' acts as a link.
(Other definitions for pea that I've seen before include "Annual climbing plant with edible seeds" , "It grows in 23 Down" , "Climber" , "Little green vegetable" , "Spherical vegetable" .)