This supports stocking revolutionary American poet (9)
I believe the answer is:
suspender
'this supports stocking' is the definition.
(suspenders hold up stockings)
'revolutionary american poet' is the wordplay.
'revolutionary' says the letters should be written backwards.
'american' becomes 'us' (abbreviation for United States).
'poet' becomes 'spender' (Stephen Spender).
'us' backwards is 'su'.
'su'+'spender'='SUSPENDER'
(Other definitions for suspender that I've seen before include "Sock support" , "Strap to hold up a stocking" , "material support" , "Stocking-holding strap" , "hanger on?" .)