Lap up wallop (4)
I believe the answer is:
lick
This clue is a double definition.
'lap up' is the first definition.
(I know that lap up can be written as lick)
'wallop' is the second definition.
(I've seen this in another clue)
(Other definitions for lick that I've seen before include "Lap; beat soundly" , "Taste" , "A - - and a promise" , "little paint" , "Flog" .)