Material that's not trendy making a comeback (5)
I believe the answer is:
ninon
'material' is the definition.
(I know that ninon is a type of material)
'not trendy making a comeback' is the wordplay.
'not' becomes 'non' (I've seen this in other clues).
'trendy' becomes 'in' ('in' can mean fashionable).
'making a comeback' says the letters should be written backwards.
'non'+'in'='nonin'
'nonin' backwards is 'NINON'.
'that's' acts as a link.
(Other definitions for ninon that I've seen before include "thin fabric" , "delicate material" , "Dressmaker" , "Fine, strong, silky fabric" , "Silk voile" .)