Sentinel (5)
'sentinel' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for guard that I've seen before include "Sentry" , "Protect(or)" , "Custodian" , "Screw" , "state of caution" .)
'sentinel' is the definition.
(I know that sentinel can be written as lookout)
This is all the clue.
(Other definitions for lookout that I've seen before include "Nightwatchman" , "Watchtower" , "View" , "Watchman" , "One keeping watch" .)