Safe with a musician? It's hard to say (5,5)

I believe the answer is:

peter piper

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'hard to say' is the definition.
I know nothing about this answer so I can't judge whether this works.

'safe with a musician?' is the wordplay.
'safe' becomes 'peter' (slang term for a safe).
'with' means one lot of letters go next to another.
'a musician?' becomes 'piper' (someone playing the bagpipes).
'peter'+'piper'='PETER PIPER'

'it's' acts as a link.

Can you help me to learn more?

I've seen this clue in The Guardian.

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