The verb ensure has 2 senses (first 2 from tagged texts)
1. (6) guarantee, ensure, insure, assure, secure -- (make certain of; "This nest egg will ensure a nice retirement for us"; "Preparation will guarantee success!")
2. (2) see, check, insure, see to it, ensure, control, ascertain, assure -- (be careful or certain to do something; make certain of something; "He verified that the valves were closed"; "See that the curtains are closed"; "control the quality of the product")