An essential, like round fruit … (7)
I believe the answer is:
satsuma
'fruit' is the definition.
(I know that satsuma is a type of fruit)
'an essential like round' is the wordplay.
'an' becomes 'a'.
'essential' becomes 'must' (similar in meaning).
'like' becomes 'as'.
'round' shows that the letters should be reversed in order.
'a'+'must'+'as'='amustas'
'amustas' written backwards gives 'SATSUMA'.
(Other definitions for satsuma that I've seen before include "that's segmented" , "Loose-skinned tangerine" , "Orange - type of pottery" , "Type of tangerine" , "Kind of tangerine" .)