Smaller in the row outside (6)
I believe the answer is:
tinier
'smaller' is the definition.
('tiny' can be similar in meaning to 'small')
'in the row outside' is the wordplay.
'the row' becomes 'tier' (a tier is a row of things).
'outside' indicates putting letters inside (some letters go outside others).
'in' placed inside 'tier' is 'TINIER'.
(Other definitions for tinier that I've seen before include "Even smaller" , "more minute?" , "Much smaller" , "much less significant?" , "More constricted" .)