A necessity when raising fruit (7)
I believe the answer is:
satsuma
'fruit' is the definition.
(satsuma is a kind of fruit)
'a necessity when raising' is the wordplay.
'necessity' becomes 'must' (I've seen this before).
'when' becomes 'as'.
'raising' says the letters should be written backwards.
'a'+'must'+'as'='amustas'
'amustas' back-to-front is 'SATSUMA'.
(Other definitions for satsuma that I've seen before include "Small, easily-peeled orange" , "that is easily uncovered" , "Segmented item" , "Easy-peeling tangerine" , "Citrus fruit from Japan" .)