Swapping leaders, get criminal boss (3,5)

I believe the answer is:

big daddy

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'boss' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'swapping leaders get criminal' is the wordplay.
'swapping leaders' becomes 'igd' (I can't explain this - if you can you should give a lot more credence to this answer).
'get' is an insertion indicator.
'criminal' becomes 'baddy' (bad guy).
'igd' put into 'baddy' is 'BIG DADDY'.

Can you help me to learn more?

(Another definition for big daddy that I've seen is " Shirley Crabtree, in the ring".)

I've seen this clue in The Times.

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