Uses a fifty, that is, to get some drinks while they just lounge there, idly (3,6)
I believe the answer is:
lie around
'while they just lounge there idly' is the definition.
The definition suggests an adverb but the answer is not.
'uses a fifty that is to get some drinks' is the wordplay.
'uses' is an anagram indicator (I've seen 'used' mean this).
'fifty' becomes 'l' (Roman numeral).
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'to get' indicates putting letters inside.
'some drinks' becomes 'round' (as in a round of drinks).
'a'+'l'='al'
'al' with letters rearranged gives 'la'.
'la' going around 'ie' is 'liea'.
'liea'+'round'='LIE AROUND'
Can you help me to learn more?
(Other definitions for lie around that I've seen before include "not placed with an order" , "Be scattered" , "Be idle" , "what the idlers do" .)