Fruit's a necessity when reflecting (7)
I believe the answer is:
satsuma
'fruit's' is the definition.
(satsuma is a kind of fruit)
'a necessity when reflecting' is the wordplay.
'necessity' becomes 'must' (I've seen this in other clues).
'when' becomes 'as'.
'reflecting' says the letters should be written backwards.
'a'+'must'+'as'='amustas'
'amustas' backwards is 'SATSUMA'.
(Other definitions for satsuma that I've seen before include "Small variety of orange similar to mandarin" , "Kind of tangerine" , "Easy-peeling tangerine" , "Orange, district and style of Japanese pottery" , "As a must (anag)" .)