Stiff material to resist something battering (7)
I believe the answer is:
buckram
'stiff material' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for buckram that I've seen before include "stiff material" , "Cloth stiffened with size" , "Coarse stuff" , "Coarse cotton fabric stiffened with glue" , "Stiffened open-weave fabric" .)