Stopping at nothing, the wealthy and powerful underworld boss (5)

I believe the answer is:

pluto

'underworld boss' is the definition.
(Roman god of the underworld)

I cannot understand how the rest of the clue works.

(Other definitions for pluto that I've seen before include "animated dog" , "Ninth planet of solar system" , "Planet beyond Neptune" , "underworld boss" , "Dwarf planet" .)

I've seen this clue in The Times.

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