Work with barrel-maker, brewing tea (9)
I believe the answer is:
cooperate
'work' is the definition.
(cooperating is a kind of working)
'with barrel-maker brewing tea' is the wordplay.
'with' is an insertion indicator.
'barrel maker' becomes 'cooper' ('cooper' can be a synonym of 'barrel maker'**).
'brewing' indicates an anagram.
'tea' anagrammed gives 'ate'.
'cooper' inserted within 'ate' is 'COOPERATE'.
(Other definitions for cooperate that I've seen before include "Work with another, be helpful" , "Work to the same end" , "Work together on a common enterprise" , "Play ball with" , "fit in with others" .)