Old gentleman is major underworld figure (6)

I believe the answer is:

osiris

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

'old gentleman is' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'gentleman' becomes 'sir' (a man may be addressed as sir).
'o'+'sir'+'is'='OSIRIS'

'major' is the link.
I am not very happy about this link. It may be part of another bit of the clue.

Can you help me to learn more?

(Other definitions for osiris that I've seen before include "one held to be divine" , "God, husband of Isis" , "Husband of Isis, father of Horus - sis or I (anag)" , "Egyptian god - sis or I (anag)" , "underworld boss" .)

I've seen this clue in The Sunday Times.

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