old hand       
noun [ C ] uk/ˌəʊld ˈhænd/ us/ˌoʊld ˈhænd/
 老手,富有经验的人
someone who is very experienced and skilled in a particular area of activity
  We should be able to trust Silva to negotiate a good deal for us - he's an old hand at the game. 们应能相信席尔瓦会为我们谈成一笔好生意——他精于此道。 
 Synonyms: old-timer veteran 
Compare: warhorse