Answer: indorsing

AnswerCrossword Clue
indorsingDeclare one's public approval or support of
indorsingRecommend (a product) in an advertisement
indorsingSign (a check or bill of exchange) on the back to make it payable to someone other than the stated payee or to accept responsibility for paying it
indorsingINDORSE, to declare one's approval, also ENDORSE
indorsingWrite (a comment) on the front or back of a document