Copied letters to the Editor (4)

I believe the answer is:

aped

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'copied' is the definition.
('ape' can be a synonym of 'copy')

'letters to the editor' is the wordplay.
'letters' becomes 'ap' (I can't explain this - if you can you should believe this answer much more).
'to the editor' becomes 'ed'.
'ap'+'ed'='APED'

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(Other definitions for aped that I've seen before include "was imitative" , "Caricatured" , "Imitated like monkey" , "Imitated in every aspect" , "Followed" .)

I've seen this clue in the Evening Standard.

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