Around Trojan, running horse may wear this (9)
I believe the answer is:
caparison
'horse may wear this' is the definition.
The definition suggests a singular noun which matches the answer.
'around trojan running' is the wordplay.
'around' becomes 'ca' (circa).
'trojan' becomes 'Paris' (mythical Trojan).
'running' becomes 'on' (eg when a machine is running it is on).
'ca'+'paris'+'on'='CAPARISON'
Can you help me to learn more?
(Other definitions for caparison that I've seen before include "Rich clothing" , "rich gear" , "Rich cloth laid over a warhorse" , "covering for the Shires?" , "Decorative covering for a horse" .)