Crossword Genius

Parent of boy who's a rascal? (3)

Ross

I believe the answer is:

gun

'parent of boy' is the definition.
'Gun' can be an answer for 'boy'. I'm not sure about the 'parent of' bit.

I cannot understand how the remainder of the clue works.

(Other definitions for gun that I've seen before include "Hired killer" , "Shooter" , "Platform from which to shoot" , "An offensive weapon" , "Throttle" .)

I've seen this clue in The Guardian.
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