Small target for bad person (6)
I believe the answer is:
sinner
'for bad person' is the definition.
(sinner is a kind of bad person)
'small target' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'target' becomes 'inner' (I've seen this before).
's'+'inner'='SINNER'
(Other definitions for sinner that I've seen before include "Transgressor of the moral law" , "person being wicked" , "One in error" , "Offender against moral law" , "One in breach of moral law" .)