Tips for narc: experts pull hot rocks on nice tube (7)

I believe the answer is:

nephron

'tube' is the definition.
(nephron is a kind of tube)

'tips for narc experts pull hot rocks on nice' is the wordplay.
'tips for' suggests taking the first letters (letters at the tips of the words).
The initial letters of 'narc experts pull hot rocks on nice' is 'NEPHRON'.

I've seen this clue in The Independent.

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