on watch for (someone or something)(redirected from on watch for one)
on watch for (someone or something)
Actively and attentively looking out for someone or something. You need to be on watch for suspicious people when you're out in the city this late at night. We've had to put extra inspectors on watch for counterfeit products being smuggled through the shipping yard.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.