Agreement about backing fabric (6)
I believe the answer is:
accord
'agreement' is the definition.
(accord is a kind of agreement)
'about backing fabric' is the wordplay.
'about' becomes 'ca' (abbreviation for 'circa'**).
'backing' is a reversal indicator.
'fabric' becomes 'cord' (cord is a kind of fabric).
'ca' reversed gives 'ac'.
'ac'+'cord'='ACCORD'
(Other definitions for accord that I've seen before include "Unanimity" , "Model" , "Official agreement; harmony" , "Agree" , "Correspond" .)