Tie Clip is a challenge to cut Donkey Mong's tie without any of the Vault Hunters present being hit by his barrels. This challenge is worth 5 Badass Rank.
Donkey Mong may be passive and will not attack unless provoked. In this case it is possible to walk near him and interact with his tie while he's alive. If Donkey Mong is aggressive for any reason, it will be necessary to evade a thrown barrel from a safe distance and run to him. Phaselock also helps this purpose.
Melee attacks do not cut the tie. Instead, players must hit the interact button (PC default E/ Xbox default X) in order to cut the tie.