Ringleader found after prisoner and copper see eye to eye (6)
I believe the answer is:
concur
'see eye to eye' is the definition.
(I've seen this before)
'ringleader found after prisoner and copper' is the wordplay.
'ringleader' becomes 'r' (first letter of ring).
'found after' says to put letters next to each other.
'prisoner' becomes 'con' (abbreviation for 'convict').
'and' is a charade indicator (letters next to each other).
'copper' becomes 'cu' (chemical symbol).
'con'+'cu'='concu'
'r' put after 'concu' is 'CONCUR'.
(Other definitions for concur that I've seen before include "Agree, assent" , "Be in accord" , "meet" , "'Agree, coincide (6)'" , "Express agreement" .)