When you publish a survey, a page will be created in your community and a link to that page will be in the community's navigation bar. If you would like to remove the survey, this is done from the Survey management area, and not the Pages CMS area.
To remove a Survey page from your community:
Go to Surveys in the Crowd Management menu
Make sure that you are viewing the list of published surveys, this is the tab that shows by default when you open the Surveys area
Click Unpublish next to the Survey that you would like to remove.
When you have unpublished the survey, it will not be visible in the community, but you are still able to see the results of the survey. To do so, go to the unpublished tab in the Surveys area and click on Results next to the relevant survey.