"To support the amendment" means to be in favor of making a change to an existing document or law. It means you agree with the proposed amendment and want it to be added or modified. Full definition
The argument that casino expansion will lead to job creation was a key argument made by campaigns supporting the amendment to expand casino gambling last year. (nystateofpolitics.com)
The SNP, which also supported the amendment, was three short of a full turn - out. (politics.co.uk)
Many of you have done so, and we hope your colleagues will join you in supporting the amendment on June 4th. (socialliberal.net)