Take loads of money and be laughing? (2,1,7,5)

I believe the answer is:

do a roaring trade

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'take loads of money and' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'laughing?' is the wordplay.
I cannot quite see how this works, but
'laughing?' could be 'roaring' (roaring is a kind of laughing) and 'roaring' is present in the answer.
This explanation may well be incorrect...

'be' is the link.

Can you help me to learn more?

I've seen this clue in The Times.

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