Wiktionary
dab hand
n. (context British English) An expert; a very skilled person.
Usage examples of "dab hand".
In view of the fact that be bad aboard some ill-disposed person who was clearly a dab hand with some of the more esoteric poisons this was as unwarrantedly optimistic a statement as I could remember making, but I had to say something.
Crewmen who'd served with Piet on his long voyages treated Guillermo as a fellow and a dab hand with a starship's controls, almost the equal of Captain Ricimer himself.
She was a dab hand at lying-ins, though I wasn't supposed to know such things.