Abstaining completely from alcohol (8)
I believe the answer is:
teetotal
'abstaining completely from alcohol' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for teetotal that I've seen before include "Never drinking alcohol" , "not taking a drop" , "Abstaining completely from alcoholic drinks" , "Taking no alcohol" , "Abstemious" .)