From West Coast state, one firm supplying cloth (6)
I believe the answer is:
calico
'cloth' is the definition.
(I know that calico is a type of cloth)
'from west coast state one firm' is the wordplay.
I cannot quite understand how this works, but
'from' could be 'o' (I've seen this in other clues) and 'o' is present in the answer.
'state' could be 'cal' (short for California) and 'cal' is present in the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
A single letter 'c' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'supplying' is the link.
Can you help me to learn more?
(Other definitions for calico that I've seen before include "Coarse printed cotton cloth" , "Plain cotton cloth, white or unbleached" , "Given material for dress" , "Cotton cloth or fabric" , "Unbleached sixteen down cloth" .)