Understanding nondrinker pocketed the bill (4)
I believe the answer is:
tact
'understanding' is the definition.
(I've seen this before)
'the bill' is the wordplay.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'bill' becomes 'act' (an Act of Parliament).
't'+'act'='TACT'
'nondrinker pocketed' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for tact that I've seen before include "Skill in dealing with people" , "measure of diplomacy?" , "Consideration and sensitivity" , "Consideration in dealing with others" , "Fine perception" .)