Leave small stuff (5)
I believe the answer is:
scram
'leave' is the definition.
(to scram is to leave somewhere quickly)
'small stuff' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'stuff' becomes 'cram' (synonyms).
's'+'cram'='SCRAM'
(Other definitions for scram that I've seen before include "beat hasty retreat" , "Clear off!" , "In slang, go away and beat it" , "Buzz off!" , "Vamoose" .)