Once more offend Amber? (5)
I believe the answer is:
resin
This clue is a double definition.
'once more offend' is the first definition.
(to sin again)
'amber?' is the second definition.
(amber is a kind of resin)
(Other definitions for resin that I've seen before include "Myrrh, for instance" , "Glue" , "Lac" , "Synthetic substance" , "Plant exudation" .)