Troops upsetting loser, Sid (8)

I believe the answer is:

soldiers

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'troops' is the definition.
Although both the answer and definition are verbs in their -s form, I can't understand how they can define each other.

'upsetting loser sid' is the wordplay.
'upsetting' is an anagram indicator.
'loser'+'sid'='losersid'
'losersid' is an anagram of 'SOLDIERS'.

Can you help me to learn more?

(Other definitions for soldiers that I've seen before include "Strips of toast for egg dipping" , "[TOAST] divided up" , "men" , "Members of the military" , "Troopers" .)

I've seen this clue in The Daily Express.

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