Colour's run with material ruined (11)
I believe the answer is:
ultramarine
'colour's' is the definition.
(ultramarine is a kind of colour)
'run with material ruined' is the wordplay.
'with' says to put letters next to each other.
'ruined' indicates anagramming the letters.
'run' after 'material' is 'materialrun'.
'materialrun' anagrammed gives 'ULTRAMARINE'.
(Other definitions for ultramarine that I've seen before include "Brilliant deep blue" , "Vivid blue" , "See a colour" , "one of the colours" , "Blue pigment originally made from lapis lazuli" .)