One refusal to drink small measure altogether (2,4)
I believe the answer is:
in toto
'altogether' is the definition.
(I've seen this before)
'one refusal to drink small measure' is the wordplay.
'one' becomes 'i' (Roman numeral).
'refusal' becomes 'no' (saying no to something).
'to drink' is an insertion indicator.
'small measure' becomes 'tot' (small measure of alcohol).
'no' enclosing 'tot' is 'ntoto'.
'i'+'ntoto'='IN TOTO'
(Other definitions for in toto that I've seen before include "overall" , "Completely - entirely (Latin)" , "Wholly" , "All told" , "Altogether, completely" .)