Very, very good to reside in pub, but pointless (2,4)
I believe the answer is:
in vain
'but pointless' is the definition.
I can't tell whether this definition defines the answer.
'very very good to reside in pub' is the wordplay.
'very' becomes 'v' (common abbreviation).
'very good' becomes 'AI' (resembles 'A1', old-fashioned term for excellent).
'to reside in' means one lot of letters goes inside another.
'pub' becomes 'inn' (an inn is a type of pub).
'v'+'ai'='vai'
'vai' inserted within 'inn' is 'IN VAIN'.
Can you help me to learn more?
(Other definitions for in vain that I've seen before include "Without effect" , "'To no avail (2,4)'" , "Uselessly, without success" , "Uselessly, to no profit" , "To no end" .)