Enter tube gnashing teeth with caries (11)

I believe the answer is:

catheterise

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

'enter tube gnashing' is the definition.
I can't judge whether this definition defines the answer.

'teeth with caries' is the wordplay.
I cannot really see how this works, but
an anagram of 'teeth' is 'thete' which is located in the answer.
an anagram of 'caries' is 'carise' which is located in the left over letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Independent.

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