I've no idea if hatmaker's one for tailoring? (3,2,7)

I believe the answer is:

ask me another

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'i've no idea' is the definition.
('ask me another' means 'I don't know')

'hatmaker's one for tailoring?' is the wordplay.
'hatmaker's one' anagrams to 'ASK ME ANOTHER'.
Though, I am unsure how this is indicated.

'if' acts as a link.

Can you help me to learn more?

I've seen this clue in The Guardian.

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