Easter setting for final Cockney (9)
I believe the answer is:
eastender
'cockney' is the definition.
(I've seen this before)
'easter setting for final' is the wordplay.
'setting for' means one lot of letters goes inside another (inserted letters are set inside others).
'final' becomes 'end' (synonyms).
'easter' enclosing 'end' is 'EASTENDER'.
(Other definitions for eastender that I've seen before include "eg Barbara Windsor" , "Cockney" , "Capital fellow" , "Someone born within the sound of Bow Bells?" , "Pearly Queen surely is" .)