There's no telling where it may lead (6,7)

I believe the answer is:

secret passage

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

'lead' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?

'there's no telling where it' is the wordplay.
I cannot quite understand how this works, but
'it' could be 'sa' (old-fashioned abbreviation for sex appeal) and 'sa' is located in the answer.
This explanation may well be incorrect...

'may' acts as a link.

Can you help me to learn more?

I've seen this clue in The Irish Independent.

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