Crossword Genius

Unsealed letter to a writer (4)

Ross

I believe the answer is:

open

'unsealed' is the definition.
(associated in meaning)

'letter to a writer' is the wordplay.
'letter' becomes 'o' ().
'to a writer' becomes 'pen' (something which writes).
'o'+'pen'='OPEN'

(Other definitions for open that I've seen before include "Plain" , "Not enclosed" , "Traditional room heater" , "Allowing entry and exit" , "Unfasten" .)

I've seen this clue in the Evening Standard.
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