Seed on top of ripe fruit (4)
I believe the answer is:
pear
'fruit' is the definition.
(I know that pear is a type of fruit)
'seed on top of ripe' is the wordplay.
'seed' becomes 'pea' (I've seen this before).
'on top of' indicates taking the first letters.
The initial letter of 'ripe' is 'r'.
'pea'+'r'='PEAR'
(Other definitions for pear that I've seen before include "Shapely fruit?" , "Tasty fruit to reap" , "Fruit; sounds like duo" , "Cider-making fruit" , "Pomaceous fruit" .)