Heartless dame with a Mafia boss? Exactly! (4,2)

I believe the answer is:

dead on

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

'heartless dame with a mafia boss?' is the wordplay.
'heartless' says to hollow out the word (remove centre letters).
'with' says to put letters next to each other.
'mafia boss?' becomes 'don' (term for a mafia leader).
'dame' with its middle removed is 'de'.
'de'+'a'+'don'='DEAD-ON'

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