Endlessly producing fruit (6)
I believe the answer is:
raisin
'fruit' is the definition.
(raisin is a kind of fruit)
'endlessly producing' is the wordplay.
'endlessly' means to remove the last letter.
'producing' becomes 'raising' ('raise' can be a synonym of 'produce').
'raising' with its final letter removed is 'RAISIN'.
(Other definitions for raisin that I've seen before include "Dried grape used in cakes" , "Large dried grape" , "fruit product" , "A dried grape used in cake" , "Dried red grape" .)