old hand

plural old hands

1. idiomaticA person who is experienced at a certain activity.

   Near-synonyms: insider, initiate; habitué

   2 more examples

   My tax advisor is an old hand at dealing with auditors.

   The media, needless to say, are very pro-Bloomberg. He’s an old hand at stroking reporters and television executives, and few of them have raised the fact that it was Rudy who inherited a lawless city with crime out of control and over eight years, via his ‘broken windows’ theory, turned Gotham into the safest big city on the planet.

   2020 March 2, Taki Theodoracopulos, “What makes Bloomie run?”, in The Spectator (US edition)

   Synonyms: veteran, warhorse, insider, initiate, habitué