Played around on horseback, braced (9)
I believe the answer is:
supported
'braced' is the definition.
(similar in meaning)
'played around on horseback' is the wordplay.
'played' becomes 'sported' (sporting is a kind of playing).
'around' is an insertion indicator.
'on horseback' becomes 'up' (up can mean up on a horse).
'sported' placed around 'up' is 'SUPPORTED'.
(Other definitions for supported that I've seen before include "Bolstered, sustained" , "cared for" , "Took sides with" .)