Competition needing horses you rent out (7)
I believe the answer is:
tourney
'competition' is the definition.
(tourney is a kind of competition)
'you rent out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'you'+'rent'='yourent'
'yourent' is an anagram of 'TOURNEY'.
'needing horses' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tourney that I've seen before include "competitive event" , "US sports event" , "Competition" .)