He'll give you a good towelling (5)
I believe the answer is:
terry
'towelling' is the definition.
(terry is a kind of towelling)
'he'll give you a good' is the wordplay.
I cannot really understand how this works, but
'good' could be 'err' (I've seen this in another clue) and 'err' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for terry that I've seen before include "Loop of pile fabric; England footballer" , "(Rhyming) man's name" , "A man" , "Fabric with piles" , "Towelling fabric" .)