Amber, say, to commit further offence? (5)
I believe the answer is:
resin
'amber' is the definition.
(I've seen this in another clue)
'to commit further offence?' is the wordplay.
'to commit further' becomes 're' (I can't explain this - if you can you should give a lot more credence to this answer).
'offence?' becomes 'sin' (a sin is an offence or transgression).
're'+'sin'='RESIN'
'say' is the link.
Can you help me to learn more?
(Other definitions for resin that I've seen before include "Sticky stuff from pine trees" , "Unprocessed pine secretion" , "Sticky substance exuded by pine trees" , "Substance from tree-sap" , "Synthetic substance" .)