Mugged fellow used to drink in pub (4,3)
I believe the answer is:
'drink in pub' is the definition.
The definition suggests a singular noun which matches the answer.
'mugged fellow used' is the wordplay.
I cannot really understand how this works, but
'fellow' could be 'toby' (I've seen this before) and 'toby' is found in the answer.
The remaining letters 'jug' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'to' is the link.
(Other definitions for toby jug that I've seen before include "Beer container" , "Man getting drunk from" , "drinking-vessel?" , "Pitcher" , "Man-shaped drinking pot" .)