Yes, that is it's foot. Typically, a healthy anemone in a healthy tank grabs on to surfaces with it's foot. Heck, healthy anemones typically grab hold of my hand as I'm moving them out and in. Unfortunately, that one looks stressed. What is the reason? I would ask how long this tank has been set up and how was it set up, what are the water parameters, especially Alk and Ca, and how does the tank look?
In summary:
Tank Age?
Filtration?
Alk?
Ca?
Nitrate?
Tank Pic?
Aloha,
Mark