Louse up in cake (6)
I believe the answer is:
muffin
'cake' is the definition.
(I've seen this before)
'louse up in' is the wordplay.
'louse up' becomes 'muff' ('muff' can be a synonym of 'louse up').
'muff'+'in'='MUFFIN'
(Other definitions for muffin that I've seen before include "baked treat" , "Thick roll, usually toasted" , "Cake - old TV mule" , "Flat, circular bread roll, eaten toasted and buttered" , "Yeast roll for toasting" .)