Crossword Genius

The schoolkids wouldn’t miss him (3)

Ross

I believe the answer is:

sir

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

'the schoolkids wouldn't miss him' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.

'him' is the wordplay.
I cannot really understand how this works, but
'him' could be 'si' and 'si' is found in the answer.
A single letter 'r' remains which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for sir that I've seen before include "Polite term of address for a man" , "Polite or formal address to male" , "Formal term of address" , "Male form of address" , "Way to address gentleman" .)

I've seen this clue in the Evening Standard.
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