plug away
phrasal verb with plug verb [ T ] uk/plʌɡ/ us/plʌɡ/ -gg-
informal
坚持不懈地做（尤指困难的事情）
to work hard and in a determined way, especially at something that you find difficult
Katie has been plugging away at her homework for hours. 凯蒂已经做了好几个小时的作业了。