Sweetheart long gone (5)

I believe the answer is:

lover

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'sweetheart' is the definition.
(sweetheart can mean a lover)

'long gone' is the wordplay.
'long' becomes 'l'.
'gone' becomes 'over' (I can't justify this - if you can you should give a lot more credence to this answer).
'l'+'over'='LOVER'

Can you help me to learn more?

(Other definitions for lover that I've seen before include "He really likes" , "Romantic partner" , "Juliet, for example" , "Beau" , "'Lady Chatterley's - - ' by D H Lawrence" .)

I've seen this clue in The Globe and Mail.

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