I don't know how complex this feature would be but I was dying for that (aswell as MANY other ableton users) and I don't think they ever implemented that.
You fill up an audio/midi clip on a pad by playing live, screw up a little bit and want to scratch that manually on your controller : You can't.. and it sucks especially in the middle of a performance.
People or forced to record on the pad bellow but then it kinda fucks up your scene cause Part A of your song (normally row 1) as one clip in row 2. If you could just hold down the pad for like 2-3 seconds to clear it, it'b awesome.
Coming from Boss Rc-300 / RC-505 and i'm sure many other loopers, this is pretty common so ppl would feel at home