Beam over such material (5)
I believe the answer is:
rayon
'material' is the definition.
(I know that rayon is a type of material)
'beam over' is the wordplay.
'beam' becomes 'ray' (synonyms).
'over' becomes 'on' (physically on top of).
'ray'+'on'='RAYON'
'such' acts as a link.
(Other definitions for rayon that I've seen before include "Artificial silk fabric" , "Semi-synthetic material" , "Synthetic material" , "Man-made fabric" , "Viscose fibre" .)