They supply brewed drinks on tap (3,4)
I believe the answer is:
tea urns
'they supply brewed' is the definition.
The definition suggests an adverb but the answer is not.
'drinks on tap' is the wordplay.
'drinks' becomes 'teas' (tea is a kind of drink).
'on' means one lot of letters goes inside another (as in clothing 'on' a person).
'tap' becomes 'urn' (I can't justify this - if you can you should believe this answer much more).
'teas' enclosing 'urn' is 'TEA-URNS'.
Can you help me to learn more?
(Other definitions for tea urns that I've seen before include "refreshments they provide" , "containers" .)