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Dad, it’s fail-safe, available and completely healthy (2,3,2,1,6)

Ross

I believe the answer is:

as fit as a fiddle

I'm a little stuck... Click here to teach me more about this clue!

'dad it's fail-safe available and completely healthy' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'dad it's fail-safe available and completely healthy' is the wordplay.
'dad it's fail-safe' can be anagrammed to 'AS FIT AS A FIDDLE'.
But, I am not clear how the anagram is indicated.

Can you help me to learn more?

(Another definition for as fit as a fiddle that I've seen is " in form!".)

I've seen this clue in the Sydney Morning Herald.
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