Drinks bought for mates -- stout! (5)
I believe the answer is:
round
I believe this clue is a double definition.
'drinks bought for mates' is the first definition.
(a round of drinks)
'stout' is the second definition.
(I've seen this before)
(Other definitions for round that I've seen before include "series of calls" , "Serving of sandwich" , "Lap" , "Drinks order" , "Like ball < in rough" .)