In barracks picked up drink (5)
I believe the answer is:
booze
'drink' is the definition.
(synonyms)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for booze that I've seen before include "intoxicating stuff" , "Drink too much (colloq.)" , "Intoxicating liquor" , "Drink heavily" , "Alcohol (colloq.)" .)