Dessert I stuff inside suit, messily (8)
I believe the answer is:
tiramisu
'dessert' is the definition.
(I've seen this before)
'i stuff inside suit messily' is the wordplay.
'stuff' becomes 'ram' (ram can mean to stuff or push).
'inside' is an insertion indicator.
'messily' indicates an anagram.
'i'+'ram'='iram'
'suit' anagrammed gives 'tisu'.
'iram' placed within 'tisu' is 'TIRAMISU'.
(Other definitions for tiramisu that I've seen before include "Italian dessert with coffee and liqueur" , "Dessert -- is it arum? (anag)" , "It. dessert, literally pick me up" , "Greek dessert" , "I must air the Italian dessert" .)