Answer: endorsing

AnswerCrossword Clue
ENDORSINGSupporter's activity
endorsingSign (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
endorsingWrite (a comment) on the front or back of a document
endorsingDeclare one's public approval or support of
endorsingRecommend (a product) in an advertisement
endorsingENDORSE, to declare one's approval, also INDORSE