Where pop is drunk in a sort of tavern (6)
I believe the answer is:
nippon
'where' is the definition.
The answer is a location as well as being a singular noun. This is suggested by the definition.
'pop is drunk in a sort of tavern' is the wordplay.
'is drunk' indicates an anagram.
'in' is an insertion indicator.
'a sort of tavern' becomes 'nin' (I can't justify this - if you can you should give a lot more credence to this answer).
'pop' anagrammed gives 'ppo'.
'ppo' put within 'nin' is 'NIPPON'.
Can you help me to learn more?
(Other definitions for nippon that I've seen before include "Transliteration of "Japan"" , "Japanese name for Japan (6)" .)