They aren't commonly forward in pubs! (6)
I believe the answer is:
barons
'they aren't commonly' is the definition.
The definition suggests an adverb but the answer is not.
'forward in pubs' is the wordplay.
'forward' becomes 'on'.
'in' is an insertion indicator.
'pubs' becomes 'bars' (a bar is a pub).
'on' inserted within 'bars' is 'BARONS'.
Can you help me to learn more?
(Other definitions for barons that I've seen before include "No bars for the British peers" , "Lords" , "Low-ranking British peers" .)