Jockeys on contract (6)
I believe the answer is:
riders
'jockeys on contract' is the definition.
'riders' can be an answer for 'jockeys' (I've seen this before). I'm not certain of the 'on contract' bit.
'jockeys on contract' is the wordplay.
'jockeys' becomes 'rides' (I've seen this in another clue).
'on' is an insertion indicator (as in clothing 'on' a person).
'contract' becomes 'r' (I can't explain this - if you can you should give a lot more credence to this answer).
'rides' placed around 'r' is 'RIDERS'.
Can you help me to learn more?
(Other definitions for riders that I've seen before include "Jockeys" , "As additions to bill" , "Equestrians" , "Clauses appended to a legislative bill" , "qualifications" .)