Old cart traps mater uncomfortably in conduit

I believe the answer is:

water main

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

'conduit' is the definition.
(water main is a kind of conduit)

'old cart traps mater uncomfortably' is the wordplay.
'old cart' becomes 'wain' (I've seen this before. I am not sure about the 'old' bit.**).
'traps' indicates putting letters inside.
'uncomfortably' is an anagram indicator.
'mater' anagrammed gives 'aterm'.
'wain' placed around 'aterm' is 'WATER-MAIN'.

'in' acts as a link.

Can you help me to learn more?

(Other definitions for water main that I've seen before include "Principal supply pipe" , "municipal service" , "Principle pipe for H2O" , "Supplier" .)

I've seen this clue in The Telegraph.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.