Something that's dried on (7)

I believe the answer is:

bathmat

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

'something that's dried' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'on' is the wordplay.
I cannot quite see how this works, but
'on' could be 'at' (I've seen this in other clues) and 'at' is found within the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Another definition for bathmat that I've seen is " this to absorb the drips?".)

I've seen this clue in The Daily Express.

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