Restriction on a nobleman (5)

I believe the answer is:

baron

'a nobleman' is the definition.
(baron is a kind of nobleman)

'restriction on' is the wordplay.
'restriction' becomes 'bar' (I've seen this in other clues).
'bar'+'on'='BARON'

(Other definitions for baron that I've seen before include "British peer of the lowest rank" , "Minor peer" , "British peer; business mogul" , "Powerful industrialist" , "Nobleman providing a portion of beef" .)

I've seen this clue in The Globe and Mail.

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