Action to start set pieces is needed, they maintain (10)

I believe the answer is:

servicemen

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'they maintain' is the definition.
The definition suggests an adverb but the answer is not.

'action to start set pieces is needed' is the wordplay.
'action to start set' becomes 'service' (tennis serve).
'pieces' becomes 'men' (man can mean a chess piece).
'is needed' is a charade indicator (letters next to each other).
'service'+'men'='SERVICEMEN'

Can you help me to learn more?

(Other definitions for servicemen that I've seen before include "Members of armed forces" , "People in the armed forces" .)

I've seen this clue in The Times.

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