Volume drunk by cold climbers not uniform (7)
I believe the answer is:
civvies
'volume drunk by cold climbers not uniform' is the definition.
I can't tell whether this definition defines the answer.
'volume drunk by cold climbers' is the wordplay.
'volume' becomes 'v' (abbreviation for volume in book titles).
'drunk by' is an insertion indicator.
'cold' becomes 'C' (eg on taps).
'climbers' becomes 'ivies' (ivies are climbing plants).
'c'+'ivies'='civies'
'v' going into 'civies' is 'CIVVIES'.
Can you help me to learn more?
(Other definitions for civvies that I've seen before include "those not in service" , "Non-uniform" , "Non-military attire" , "Non-military clothes for ex-army personnel" , "Mufti" .)