Resist royal marines about one material (7)
I believe the answer is:
buckram
'material' is the definition.
(I know that buckram is a type of material)
'resist royal marines about one' is the wordplay.
'resist' becomes 'buck' (as in bucking a trend).
'royal marines' becomes 'RM' (abbreviation).
'about' indicates putting letters inside.
'one' becomes 'a' (a thing is one thing).
'rm' going around 'a' is 'ram'.
'buck'+'ram'='BUCKRAM'
(Other definitions for buckram that I've seen before include "Cloth stiffened with size" , "stiff stuff!" , "Coarse stiffened cloth" , "Coarse stuff" , "stiff material" .)