: the work someone is doing now I need to concentrate on the task at hand.

Do you have something to hand or at hand?

The expressions 'at hand' and 'in hand' have literal meanings. To have something at hand is to have it conveniently near you. I always keep a dictionary at hand. When you are working in the kitchen, you must have a fire extinguisher at hand.

What is the word for doing tasks?

Some common synonyms of perform are accomplish, achieve, discharge, effect, execute, and fulfill.