Satisfied infantryman took charge (8)

I believe the answer is:

gruntled

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'satisfied' is the definition.
The definition and answer can be both to do with human feelings as well as being past participle verbs.
Perhaps there's a link between them I don't understand?

'infantryman took charge' is the wordplay.
'infantryman' becomes 'grunt' (I've seen this in another clue).
'took charge' becomes 'led' (lead can mean to take charge).
'grunt'+'led'='GRUNTLED'

Can you help me to learn more?

(Another definition for gruntled that I've seen is " Happy".)

I've seen this clue in The Independent.

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