See check applied to the Spanish material (6)
I believe the answer is:
velvet
'material' is the definition.
(velvet is a kind of material)
'see check applied to the spanish' is the wordplay.
'see' becomes 'v' (Latin 'vide', used to direct a reader to a source).
'check' becomes 'vet' (I've seen this before).
'applied to' is a charade indicator (letters next to each other).
'the spanish' becomes 'el'.
'vet' put after 'el' is 'elvet'.
'v'+'elvet'='VELVET'
(Other definitions for velvet that I've seen before include "Fabric with thick soft pile" , "Fabric with short, soft pile" , "Smooth, soft fabric" , "Luxurious fabric; antler covering" , "Plush-like fabric" .)