Non-drinker (11)
I believe the answer is:
teetotaller
'non-drinker' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for teetotaller that I've seen before include "no supper!" , "One abstaining from alcohol" , "One dry" , "Abstainer from drink" , "Abstainer from alcohol" .)