Rogue whose father is liable to be fired (3,2,1,3)

I believe the answer is:

son of a gun

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'rogue' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for son of a gun that I've seen before include "Maybe Billy the Kid's issue" , "expression of surprise" , "Rogue (with a shooter for a father?)" , "Address, in the US" , "Rascal" .)

I've seen this clue in the Evening Standard.

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