Copy a letter out, being backward (3)

I believe the answer is:

coy

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'being backward' is the definition.
(thesaurus)

'copy a letter' is the wordplay.
'copy' becomes 'co' (I can't justify this - if you can you should believe this answer much more).
'a letter' becomes 'y'.
'co'+'y'='COY'

'out' is the link.
I am not very happy about this link. It may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for coy that I've seen before include "Reserved" , "not forthcoming" , "Pretending modesty" , "Pretending shyness" , "Demure, like Marvell's mistress" .)

I've seen this clue in the Evening Standard.

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