This PM, latterly? (7)

I believe the answer is:

tonight

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'this pm latterly?' is the definition.
The answer and definition can be both related to time as well as being singular nouns.
Maybe they are linked in a way I don't understand?

This is all the clue.

Can you help me to learn more?

(Other definitions for tonight that I've seen before include "Selection from West Side Story" , "Hotting (anag.)" , "song from West Side Story" , "Dark time ahead" , "the coming time for retirement" .)

I've seen this clue in The Daily Express.

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