Agree to deceive copper, right (6)
I believe the answer is:
concur
'agree' is the definition.
('concur' can be a synonym of 'agree')
'deceive copper right' is the wordplay.
'deceive' becomes 'con' (I've seen this before).
'copper' becomes 'cu' (chemical symbol).
'right' becomes 'r' (common abbreviation).
'con'+'cu'+'r'='CONCUR'
'to' is the link.
(Other definitions for concur that I've seen before include "meet" , "share the same opinion" , "See eye to eye" , "Agree, assent" , "Give assent" .)