B1
an attempt to do something
Dictionary examples:
In an effort to learn English, he watched 'The Fast and the Furious' 100 times. (0.0)
In an effort to save time, I put toothpaste on my sandwich instead of mayonnaise. (0.0)
My cat made an effort to catch the red dot, but it was just a laser pointer. (0.0)
If we could all make an effort to keep this office neater it would help. (31.7)
He's jogging around the park every morning in an effort to get in shape for the football season. (34.5)
In their efforts to reduce crime the city has expanded the police force. (39.7)