Fruit is seen in the fall (6)
I believe the answer is:
raisin
'fruit' is the definition.
(raisin is a kind of fruit)
'is seen in the fall' is the wordplay.
'seen in' is an insertion indicator.
'the fall' becomes 'rain' (I've seen this before).
'is' put inside 'rain' is 'RAISIN'.
(Other definitions for raisin that I've seen before include "Large dried grape" , "Fruit for the Christmas cake" , "Cultivating" , "sultana, say" , "Dried grape used in cakes" .)