A knight in royal household running for herald (7)

I believe the answer is:

courant

'running for herald' is the definition.
(term in heraldry)

'a knight in royal household' is the wordplay.
'knight' becomes 'n' (chess abbreviation).
'in' indicates putting letters inside.
'royal household' becomes 'court'.
'a'+'n'='an'
'an' placed within 'court' is 'COURANT'.

(Another definition for courant that I've seen is " running on coat of arms".)

I've seen this clue in The Guardian.

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