Inventor with a non-drinker (4)
I believe the answer is:
watt
'inventor' is the definition.
(I've seen this before)
'with a non-drinker' is the wordplay.
'with' becomes 'w' (abbreviation).
'non drinker' becomes 'tt' (Teetotaller abbreviation).
'w'+'a'+'tt'='WATT'
(Other definitions for watt that I've seen before include "Unit of power - Scottish inventor" , "James - - (Scottish inventor)" , "Worker in steam" , "Scottish engineer and inventor, d. 1819" , "Scot. engineer; unit of power" .)