Chaps in hail holding up a contract (9)
I believe the answer is:
agreement
'contract' is the definition.
(a contract is a legal agreement)
'chaps in hail holding up a' is the wordplay.
'chaps' becomes 'men' (chap means a man).
'in' indicates putting letters inside.
'hail' becomes 'greet' (I've seen this in another clue).
'holding up' means one lot of letters go next to another (some letters go underneath or hold up others).
'men' placed inside 'greet' is 'greement'.
'greement' after 'a' is 'AGREEMENT'.
(Other definitions for agreement that I've seen before include "Contract or promise" , "concert" , "Harmony, concurrence" , "State of being consistent" , "legal contract maybe" .)