Insect getting stuck into simple fruit (8)
I believe the answer is:
plantain
'fruit' is the definition.
(I've seen this before)
'insect getting stuck into simple' is the wordplay.
'insect' becomes 'ant' (ant is a kind of insect).
'getting stuck into' means one lot of letters goes inside another.
'simple' becomes 'plain' (associated in meaning).
'ant' put within 'plain' is 'PLANTAIN'.
(Other definitions for plantain that I've seen before include "Sort of banana" , "Shrub; green banana" , "Coarse banana" , "Tropical food" , "Low-growing plant; type of banana" .)