Is mum giving permission? (3-2)

I believe the answer is:

say-so

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'giving permission?' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for say-so that I've seen before include "Authority to make a decision" , "Final approval" , "Authorisation" , "Go-ahead" , "Authority to make or allow something to happen" .)

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