Top lady entertained by excellent boozers (6)
I believe the answer is:
topers
'boozers' is the definition.
(both can mean excessive drinkers of alcohol)
'top lady entertained by excellent' is the wordplay.
'top lady' becomes 'er' (Elizabeth Regina, Queen Elizabeth).
'entertained by' means one lot of letters goes inside another (I've seen this in other clues).
'excellent' becomes 'tops' (I've seen this before).
'er' going within 'tops' is 'TOPERS'.
(Other definitions for topers that I've seen before include "Habitual imbibers" , "Heavy drinkers" , "We regularly knock it back" .)