To which, one might be called for a drink (3,3)
I believe the answer is:
the bar
'to which one' is the definition.
I can't tell whether this defines the answer.
'might be called for a drink' is the wordplay.
'might' is an anagram indicator (I've seen this in other clues).
'called for' becomes 'thar' (I can't explain this - if you can you should give a lot more credence to this answer).
'a drink' means one lot of letters goes inside another.
'be' is an anagram of 'eb'.
'eb' placed into 'thar' is 'THE BAR'.
Can you help me to learn more?
(Other definitions for the bar that I've seen before include "Barristers collectively" , "Legal advocates are called to it" .)