Reported sudden increase in material (5)
I believe the answer is:
serge
'material' is the definition.
(serge is a kind of material)
'reported sudden increase' is the wordplay.
'reported' indicates a 'sounds like' (homophone) clue.
'sudden increase' becomes 'surge' (a surge is a sudden increase in something).
'surge' is a homophone of 'SERGE'.
'in' acts as a link.
(Other definitions for serge that I've seen before include "Frenchman" , "Material to suit" , "Twilled fabric; name" , "Stuff" , "Twilled woollen fabric" .)