From Longman Dictionary of Contemporary Englishkeep guard/watchkeep guard/watchPROTECTCAREFULto guard a place or watch around you all the time → keep
Examples from the Corpus
keep guard/watch• I told my friend Bridget it was up to us to keep watch.• Mcduff came with him to sit in the shelves and they took it in turns to keep watch.• Now do stuff that will make us want to keep watching.• The trick was to keep watching.• Capshaw sent him out the back door to avoid whoever it was keeping guard in the front.• He kept watching out the window of the rear door.• Its highly flexible neck enables it to keep watch over a wide area while it is both searching for and chasing prey.• He climbed to the top of the fence and looked around to see if there was some one keeping watch there as well. 