Disposition of a vanguard force at the Queen’s disposal (5-3-6)

I believe the answer is:

grace-and-favour

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'the queen's disposal' is the definition.
The definition suggests a singular noun which matches the answer.

'disposition of a vanguard force' is the wordplay.
'disposition of' indicates an anagram (I've seen 'disposition' mean this).
'a'+'vanguard'+'force'='avanguardforce'
'avanguardforce' with letters rearranged gives 'GRACE-AND-FAVOUR'.

'at' acts as a link.

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I've seen this clue in The Independent.

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