A question cut short interrupting very old cowboy (7)

I believe the answer is:

vaquero

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'cowboy' is the definition.
(vaquero is a kind of cowboy)

'a question cut short interrupting very old' is the wordplay.
'question' becomes 'qu'.
'cut short' becomes 'er' (I can't justify this - if you can you should believe this answer much more).
'interrupting' means one lot of letters goes inside another.
'very' becomes 'v' (abbreviation).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'a'+'qu'+'er'='aquer'
'v'+'o'='vo'
'aquer' placed within 'vo' is 'VAQUERO'.

Can you help me to learn more?

(Another definition for vaquero that I've seen is " Cowboy".)

I've seen this clue in The Telegraph.

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