In short, shouldn't he be called 'Serge'?

I believe the answer is:

sarge

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'in short shouldn't he' is the definition.
'Sarge' can be an answer for 'he'. I am not sure about the 'in short shouldn't' bit.

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for sarge that I've seen before include "NCO (colloq.)" , "Local police officer" .)

I've seen this clue in the Evening Standard.

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