Crossword Genius

Idiot senior citizen at last turning up the volume (3)

Ross

I believe the answer is:

oaf

'idiot' is the definition.
(I've seen this in another clue)

I don't understand the remainder of the clue.

(Other definitions for oaf that I've seen before include "Goon" , "Stupid lout" , "A clumsy boor" , "Lout; dolt" , "Stupid or boorish man" .)

I've seen this clue in The Independent.
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