Small feline to get lost (4)
I believe the answer is:
scat
'get lost' is the definition.
(informal imperative meaning 'go away')
'small feline' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'feline' becomes 'cat' (cat is a kind of feline).
's'+'cat'='SCAT'
'to' acts as a link.
(Other definitions for scat that I've seen before include "way to sing > "Go away!"" , "Improvised jazz singing" , "Bolt" , "Dropping" , "Jazz-singing" .)