Leather horse displayed in compound (6)
I believe the answer is:
oxhide
'leather' is the definition.
(type of leather)
'horse displayed in compound' is the wordplay.
'horse' becomes 'h' (synonyms).
'displayed in' indicates putting letters inside.
'compound' becomes 'oxide' (oxide is a kind of compound).
'h' inserted within 'oxide' is 'OXHIDE'.
(Other definitions for oxhide that I've seen before include "Type of leather" , "It's very tough" , "Neat wrapper" , "neat cover" .)