Giggle where teetotaller in row (6)
I believe the answer is:
titter
'giggle' is the definition.
(synonyms)
'teetotaller in row' is the wordplay.
'teetotaller' becomes 'tt' (abbreviation).
'in' is an insertion indicator.
'row' becomes 'tier' (tier is a kind of row).
'tt' put into 'tier' is 'TITTER'.
'where' is the link.
(Other definitions for titter that I've seen before include "Stifled laugh" , "Nervously restrained laugh" , "Nervous restrained laugh" , "A high-pitched nervous laugh" , "Silly little laugh" .)