O for some romantic correspondence! (4,6)

I believe the answer is:

love letter

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'some romantic correspondence' is the definition.
(romantic bit of correspondence)

'o for' is the wordplay.
'o' becomes 'love' (I've seen this in other clues).
'for' becomes 'letter' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'love'+'letter'='LOVE-LETTER'

Can you help me to learn more?

(Other definitions for love letter that I've seen before include "caring note!" , "romantic reading material" , "Billet-doux" .)

I've seen this clue in The Times.

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