Non-drinker in row causes giggle (6)
I believe the answer is:
titter
'giggle' is the definition.
(synonyms)
'non-drinker in row' is the wordplay.
'non drinker' becomes 'tt' (Teetotaller abbreviation).
'in' means one lot of letters goes inside another.
'row' becomes 'tier' (tier is a kind of row).
'tt' placed into 'tier' is 'TITTER'.
'causes' acts as a link.
(Other definitions for titter that I've seen before include "Stifled giggle" , "Suppressed snigger" , "Nervous or affected laugh" , "Silly little laugh" , "Chuckle" .)