remain on guard(redirected from remain on their guard)
remain on guard
To continue to be especially careful, vigilant, or attentive; to stay prepared for danger or surprises. A possessive pronoun can be used between "on" and "guard." We'll have to remain on our guard while we're in this part of the city. I want you to remain on guard while I go inside and scope the place out.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.