Fabric light with no backing (5)
I believe the answer is:
rayon
'fabric' is the definition.
(rayon is a kind of fabric)
'light with no backing' is the wordplay.
'light' becomes 'ray' (ray is a kind of light).
'with' says to put letters next to each other.
'backing' says the letters should be written in reverse.
'no' written backwards gives 'on'.
'ray'+'on'='RAYON'
(Other definitions for rayon that I've seen before include "Artificial material" , "Cellulose textile fibre" , "Artificial silk fabric" , "Man-made fibre" , "Man-made fabric" .)