The boyfriend left when finished (5)

I believe the answer is:

lover

I'm a little stuck... Click here to teach me more about this clue!

'the boyfriend' is the definition.
(boyfriend is a type of lover)

'left when finished' is the wordplay.
'left when' becomes 'l' (common abbreviation. I am not sure about the 'when' bit.).
'finished' becomes 'over' (over can mean finished or ended).
'l'+'over'='LOVER'

Can you help me to learn more?

(Other definitions for lover that I've seen before include "One of a couple" , "finished litre first" , "Suitor" , "Boyfriend" , "admirer" .)

I've seen this clue in the Evening Standard.

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