In getting a plant substance, commit another offence (5)
I believe the answer is:
resin
'in getting a plant substance commit' is the definition.
I can't tell whether this definition defines the answer.
'another offence' is the wordplay.
'another' becomes 're' (I've seen this in other clues).
'offence' becomes 'sin' (I've seen this before).
're'+'sin'='RESIN'
Can you help me to learn more?
(Other definitions for resin that I've seen before include "Very important part of plastics industry" , "It exudes from pines" , "Cannabis, say" , "hashish, say" , "component of varnish" .)