Plan to drink Bass queen filled to the top (5)
I believe the answer is:
abrim
'filled to the top' is the definition.
(I've seen this in another clue)
'plan to drink bass queen' is the wordplay.
'plan' becomes 'aim' (aiming is a kind of planning).
'to drink' is an insertion indicator.
'bass' becomes 'b' (musical abbreviation).
'queen' becomes 'r' (abbreviation for regina, e.g. in ER ).
'b'+'r'='br'
'aim' placed around 'br' is 'ABRIM'.
(Other definitions for abrim that I've seen before include "Spilling over" , "Completely full" .)