endorser
noun [ C ]
uk/ɪnˈdɔːsər/ us MARKETING
someone, especially a well-known person, who appears in an advertisement saying that they use and like a particular product:
The footballer is the company's first male celebrity endorser.
someone who makes a public statement saying that they support someone or something:
The senator is the most recent of his candidacy endorsers.
endorser of sth High-profile endorsers of the campaign include the Foreign Secretary and the chairman of the National Farmers Union.
BANKING
the person who signs the back of a cheque, bill of exchange, etc. written out to them in order to give permission for it to be paid to someone else:
If a note has been endorsed, never agree to an extension of time without getting the written consent of the endorser.