What it the word that means when you send a lead man out to lure away the enemy, police, etc?

Scout, lure, entrapment, ensnarement, inveiglement, snare, entice, seducer, drawer,

A man who gets sent ahead to check may best be described as a scout.

Snare and entrap seem the closest words found to answer your main question.

That person is sent out as a diversion.

sidetrack, divert, confuse, addle, befuddle, disturb, distract, bait-and-hook, absorb, engross and engage are the only words the come to mind. hope it was helpful.