Detective Murphy talking — he's in sole charge (8)

I believe the answer is:

dictator

'he's in sole charge' is the definition.

'detective murphy talking' is the wordplay.
I cannot really understand how this works, but
'detective' could be 'di' (Detective Inspector abbreviation) and 'di' is present in the answer.
This may be the basis of clue (or it may be nonsense).

(Other definitions for dictator that I've seen before include "Authoritarian, tyrant" , "One who reads out for others to scribe" , "Despot" , "Tyrant or oppressor" , "Hitler was one, like Stalin and Franco" .)

I've seen this clue in The Guardian.

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