Place it as the reaction beat right before a response clip in your edit. Follow it with Ceeday Huh when confusion takes over, or cut to No No Wait Wait if the hesitation turns into frantic backtracking instead.
このサウンドについて
This clip is a single drawn-out ehmmm, a hesitant vocal sound lasting about one second with no other words or effects. It gives a listener an awkward, stalled feeling, like someone buying time while searching for an answer and coming up empty in the moment.