a Johnny-come-lately

a Johnny-come-lately

  (old-fashioned)
someone who has only recently started a job or activity and has suddenly become very successful She denies suggestions that she's a Johnny-come-lately, saying that she has worked for years to get her own show.
References in periodicals archive ?
The cant and hypocrisy from a Johnny-come-lately who was parachuted into his seat to replace an ineffectual MP is amazing.
In terms of their Lordships, he is a johnny-come-lately.
The Republican Party, on the other hand, is a Johnny-come-lately taking direction from neocon interlopers while looking for support from the growing segment of the American public that has little appreciation of its own heritage of constitutionally limited government.
Friedman, who is apparently a Johnny-come-lately to the problem of our public schools, has written a very uninformed article.