Certain to stop drink being quantified (8)
I believe the answer is:
measured
'being quantified' is the definition.
(thesaurus)
'certain to stop drink' is the wordplay.
'certain' becomes 'sure' (synonyms).
'to stop' indicates putting letters inside (stopping can mean blocking a gap).
'drink' becomes 'mead' (mead is a kind of drink).
'sure' placed into 'mead' is 'MEASURED'.
(Other definitions for measured that I've seen before include "Unhurried and with care and dignity" , "Made sure (anag.)" , "Calculated, quantified" , "certain content of alcohol" , "Deliberate, restrained" .)