Coarse stuff upset farm animal (7)
I believe the answer is:
buckram
'coarse stuff' is the definition.
(type of coarse linen)
'upset farm animal' is the wordplay.
'upset farm' becomes 'buck' (I can't explain this - if you can you should give a lot more credence to this answer).
'animal' becomes 'ram' (a male sheep).
'buck'+'ram'='BUCKRAM'
Can you help me to learn more?
(Other definitions for buckram that I've seen before include "Bookbinding material - cub mark (anag)" , "Coarse stuff" , "stiff material" , "Cloth stiffened with size" , "Rough fabric sized to be stiff" .)