Ichidan verb, Intransitive verb
to endeavor (to do); to endeavour; to try hard; to work hard; to strive; to make an effort; to exert oneself; to devote oneself; to be committed (to doing)
お手伝いさんたちは主人の命令を実行しようと努めた。The servants tried to carry out their master's order.
Also written 勉める【つとめる】、力める【つとめる】