California city dropped model for female to harden (7)

I believe the answer is:

calcify

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

'harden' is the definition.
(calcifying is a kind of hardening)

'california city dropped model for female' is the wordplay.
I cannot really understand how this works, but
'california' could be 'cal' (short for California) and 'cal' is present in the answer.
'female' could be 'f' (common abbreviation) and 'f' is present in the answer.
This explanation may well be incorrect...

'to' acts as a link.

Can you help me to learn more?

(Another definition for calcify that I've seen is " Convert into lime".)

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

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