Trapped by exorbitant contract, church mounted competition (12)
I believe the answer is:
steeplechase
'competition' is the definition.
(I know that steeplechase is a type of horse race)
'trapped by exorbitant contract church mounted' is the wordplay.
I cannot quite understand how this works, but
'exorbitant' could be 'steep' (synonyms) and 'steep' is found within the answer.
'church' could be 'ch' (common abbreviation) and 'ch' is located in the answer.
'contract' could be 'lease' (leasing is a kind of contracting) and 'lease' is found within the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for steeplechase that I've seen before include "Horse race with jumps and ditches" , "Maybe Grand National" , "Race with obstacles to be jumped" , "run?" , "Non-flat horse race" .)