You can use would-be to describe someone who wants or attempts to do a particular thing. For example, a would-be writer is someone who wants to be a writer.
例句
...a book that provides encouragement for would-be writers who cannot get their novel into print.一本勉励想成为作家却不能将小说付梓者的书...a would-be rock star.想成为摇滚明星的人
英英词典释义
Adjective
1. seeking advancement or recognition
2. unfilled or frustrated in realizing an ambition