When two fighters swing the same attack tier (M1 vs M1, M2 vs M2) at nearly the same time, their attacks can clash (grapple). Both fighters are locked in place clinching each other for a short period, the fighter with the longest M1 combo leading to the grapple wins, and shoves the other back with negated damage.
A clash is not a grab. Grabs were reverted on September 21 to grab-and-punch. The wiki bind is Y / LB+RB; Discord also listed Middle Click. Mash STRUGGLE to break free. Winning a clash also gives +5 Respect; losing one is −3.