Wiktionary
just a second
interj. (context idiomatic English) stop; wait. Used to indicate that the speaker wishes the previous speaker or the proceedings to stop so that he or she can comment on what has been said or has happened so far. n. 1 (context literally English) Only one second; a passage of time one-sixtieth of a minute in duration. 2 (context idiomatic English) A short period of time, typically anywhere from a few seconds to several minutes or more.
Usage examples of "just a second".
Stars whirled by in a dizzy blur, then she released the joystick for just a second.
It throws a most interesting sidelight on Brownlee's theory of - `Just a second, Doc,' she interrupted.