In clean flight on the configuration tab near the bottom of the page is "Receiver failsafe" you check the box then set a throttle value. I use to set a throttle value that was just below hover to bring the quad down slow, however it was brought to my attention that this could A) cause the quad to drift away on dissent and make finding it harder and B) cause an esc fire potentially if a prop /motor were to get jammed up(unlikely but better safe than sorry). So now i set mine to 1000 below the minimum value that starts the motor spinning.
What is your Rx going to do when it loses Tx signal ?