put your neck on the line
put (one's) neck on the line
To personally assume or expose oneself to some risk, danger, or responsibility; to imperil oneself or put oneself in harm's way. Look, I'm putting my neck on the line for you here. I could get fired if they find out what we're up to! You have to take some risks to be successful in business and in life, but don't put your neck on the line for no good reason.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
put your neck on the linemainly BRITISH or
put your ass on the lineAMERICAN, INFORMAL, RUDE
If you put your neck on the line, you do something although it has large personal risks for you. He put his neck on the line to make the movie. I appreciate your putting your ass on the line for me. Note: You can also say that your neck is on the line or your ass is on the line to say that you will be punished or put in a bad situation if something fails. The captain's neck is on the line after this latest defeat. Note: You can also say that someone puts their ass on the line. I'm not gonna put my ass on the line for him.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012