Of the 3 Time Attack missions, you can only net this trophy on the first.
And you need to be quick, learn the map (since mini-map is disabled) and ignore EVERYONE.
There are 4 areas you need to get through, with the last area you need to clear of all enemies (3 Red Guards).
I did it with maxed out Final Ichigo, mainly because his ignition move will literally stop the clock
Below is a link that demonstrates the map layout, where the ignition boost is (because you will need it) and where a majority of the annoying enemies drop in on screen. Credit goes to ChaosVincentVII: