You know that 逃げる is "to flee" or "to run away." This is when you do fleeing to someone else. You let them go, or you let them escape, making this to let go or to let escape.

Here's a mnemonic to remember the kun'yomi for this word: There's someone you really like but you have to let go. Why? Because this school's policy is no guys (のが)! You should just set him free now, because you aren't allowed to be together here.