shop steward
noun /ˌʃɒp ˈstjuːəd/
  /ˌʃɑːp ˈstuːərd/
(especially British English)- a person who is elected by members of a trade union in a factory or company to represent them in meetings with managers- She was elected a shop steward.
 Oxford Collocations DictionaryShop steward is used after these nouns:- union