Breaking news: yellow regularly ignored in material (5)
I believe the answer is:
nylon
'material' is the definition.
(nylon is a kind of material)
'breaking news yellow regularly ignored' is the wordplay.
'breaking' means one lot of letters goes inside another.
'news' becomes 'nn' (an abbreviation for new written twice).
'regularly ignored' means one should take alternating letters (letters removed at regular intervals).
The alternating letters of 'yellow' are 'ylo'.
'nn' placed around 'ylo' is 'NYLON'.
'in' acts as a link.
(Other definitions for nylon that I've seen before include "Synthetic fabric invented in 1938" , "Hosiery material" , "Strong, resilient, synthetic fibre" , "Artificial material" , "Cover for leg" .)