Walk like a small monster (6)
I believe the answer is:
stroll
'walk' is the definition.
(I know that stroll is a type of walk)
'small monster' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'monster' becomes 'troll' (troll is a kind of monster).
's'+'troll'='STROLL'
'like a' is the link.
(Other definitions for stroll that I've seen before include "A casual or leisurely walk" , "Gentle walk" , "Saunter in no particular direction" , "Walk slowly and idly" , "A quiet, pleasant walk" .)