Safe dog held by witness (6)
I believe the answer is:
secure
'safe' is the definition.
(I know that safe can be written as secure)
'dog held by witness' is the wordplay.
'dog' becomes 'cur' (both can mean a despicable person).
'held by' is an insertion indicator.
'witness' becomes 'see' (synonyms).
'cur' placed into 'see' is 'SECURE'.
(Other definitions for secure that I've seen before include "Free from danger and financially sound" , "Incapable of being tampered with" , "Stable" , "Rescue (anag) - make safe" , "Safe against attack or intrusion" .)