A colleague stops beside your desk just as you are working through a difficult section. They may need two minutes or twenty. You cannot tell from "Have you got a second?" and a distracted conversation may leave both tasks unfinished.
Ask what they need. If it can wait, give a specific time when you can listen properly. "I'm finishing this section. Can we talk at eleven?" is easier to use than a promise to catch them later.
Keep urgent exceptions visible
If the issue is urgent, ask what must happen before your planned conversation. There may be a quick fact you can supply now while leaving the larger discussion for later. Sometimes the whole interruption really does need immediate attention.
When you return to the original task, read a brief note of where you stopped. If interruptions become routine, discuss a shared way to flag urgency and book questions. The arrangement needs to fit the people and work around you; a return time only helps when you keep it.
