Design for floor covering (6)
I believe the answer is:
format
'design' is the definition.
(thesaurus)
'for floor covering' is the wordplay.
'floor covering' becomes 'mat' (mat is a kind of floor covering).
'for'+'mat'='FORMAT'
(Other definitions for format that I've seen before include "Broadsheet or tabloid, say" , "Prepare (a disk) for data" , "Way in which something is presented" , "Shape and style as of book" , "Secure firmly in position" .)