1] Make sure Quantise to frames is switched on.

2] Expand Clip/Event View to get till you get Frame level. That's Expand not Stretch!

Then either . .

C] At front of Clip/Event grab leading edge and pull back one frame

B] Away from leading edge locate frame and srub right by 1 frame, hit splt "S" key and delete,

C] At trailing edge of Clip/Event grab final frame edge and pull back one frame left

I find A, B or C the easiest. Others may have their own methods.

Grazie