Insect burrowing into unvariegated banana (8)
I believe the answer is:
plantain
'banana' is the definition.
(plantain is a kind of banana)
'insect burrowing into unvariegated' is the wordplay.
'insect' becomes 'ant' (ant is a kind of insect).
'burrowing into' is an insertion indicator.
'unvariegated' becomes 'plain'.
'ant' placed into 'plain' is 'PLANTAIN'.
(Other definitions for plantain that I've seen before include "Shrub; green banana" , "Low-growing plant; type of banana" , "Tropical food" , "Sort of banana" , "Cooking banana" .)