Check through rental agreement after expensive race (12)
I believe the answer is:
steeplechase
'race' is the definition.
(steeplechase is a kind of race)
'check through rental agreement after expensive' is the wordplay.
'check' becomes 'ch' (I've seen this in other clues).
'through' means one lot of letters goes inside another (I've seen this in other clues).
'rental agreement' becomes 'lease' (I've seen this before).
'after' says to put letters next to each other.
'expensive' becomes 'steep' (I've seen this before).
'ch' placed inside 'lease' is 'lechase'.
'lechase' put after 'steep' is 'STEEPLECHASE'.
(Other definitions for steeplechase that I've seen before include "Type of horse race" , "Race with obstacles to be jumped" , "Maybe Grand National" , "Horse race with jumps and ditches" , "run?" .)