Definitions of collar:

• noun:   a figurative restraint

  Example: "Asked for a collar on program trading in the stock market"

• noun:   a band that fits around the neck and is usually folded over
• noun:   a band of leather or rope that is placed around an animal's neck as a harness or to identify it
• noun:   necklace that fits tightly around a woman's neck
• noun:   the act of apprehending (especially apprehending a criminal)

  Example: "The policeman on the beat got credit for the collar"

• verb:   take into custody
• verb:   furnish with a collar

  Example: "Collar the dog"

• verb:   seize by the neck or collar
• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #14371)