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.
put one's neck on the line
Fig. to put oneself at great risk. I put my neck on the line and recommended you for the job, and now look what you've done! I'm ruined!