Aware of boozer drinking round (2,2)
I believe the answer is:
in on
'aware of' is the definition.
(you can be 'in on' a particular plan or scheme)
'boozer drinking round' is the wordplay.
'boozer' becomes 'inn'.
'drinking' means one lot of letters goes inside another (inserted letters are consumed or drunk).
'round' becomes 'o' (round can mean a round object).
'inn' placed around 'o' is 'IN ON'.
(Other definitions for in on that I've seen before include "Sharing with" , "Aware of secret" , "Participating in - knowing about" , "Aware of - being part of" , "Privy to" .)