Material didn’t stand out (5)
I believe the answer is:
satin
'material' is the definition.
(satin is a kind of material)
'didn't stand out' is the wordplay.
'didn't stand' becomes 'sat' (sitting as opposed to standing).
'out' becomes 'in' (I can't explain this - if you can you should believe this answer much more).
'sat'+'in'='SATIN'
(Other definitions for satin that I've seen before include "Silk fabric" , "Stain on silky cloth" , "Shiny solk" , "Saint (anag.)" , "Material with glossy front and dull back" .)