During the morning, in the forenoon (4,8)

I believe the answer is:

ante meridiem

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

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for ante meridiem that I've seen before include "Before noon" , "A.M. in full" , "in the morning" .)

I've seen this clue in The Times.

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