Fabric stiffener (6)
I believe the answer is:
starch
'fabric stiffener' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for starch that I've seen before include "Stiffness of manner" , "Stiffening agent" , "Stiffener in the laundry" , "Charts (anag) - formality" , "Formality - give stiffness" .)