reopener
/ˌriːˈəʊp(ə)nə/ /riˈəʊp(ə)nə/originally US
noun
1A person who or thing which opens something again.
2Chiefly in industrial relations: a clause in a contract, typically between a union and management, which allows for the reopening of negotiations within the term of the contract.
Origin
Mid 19th century; earliest use found in Alexander Beresford-Hope (1820–1887), politician and author. From reopen + -er.