to tell someone in authority about something bad that someone has done because you want to cause trouble for them.

She wasn't very popular at school - she was the sort of kid who was always telling tales about other kids. (often + about)

I had half a mind to tell my boss about him but I didn't want her to think I was telling tales.

• take up on something
• take up something
• take up somewhere
• take up the cudgels against
• take up the cudgels against someone
• take up the cudgels against something
• take up the cudgels for
• take up the cudgels for someone
• take up the cudgels for something
• take up the gauntlet
• take up the reins
• take up the slack
• take up where left off
• take up where someone left off
• take up where something left off
• take up with
• take up with someone
• take with a grain of salt
• take with a pinch of salt
• take word for it
• take years off
• take years off someone
• take you back
• take you back to
• take you back to something