hold (one) at arm's length

To keep one at a certain distance away, either physical or figurative, in order to afford a level of safety or security or to prevent intimacy. John always holds his friends at arm's length, so that no one gets close enough to hurt his feelings. My daughter likes to watch me cook, but I make sure to hold her at arm's length so she doesn't get close to anything hot. I'm trying to hold Todd at arm's length so he doesn't get the wrong idea and think I'm romantically interested in him!