Stretch the Arms & Traps in the Pull
As you pull in a snatch or clean, imagine letting the weight of the bar pull your shoulders down and stretch your arms long.
A way to feel this concept is to run a band behind your traps from hand to hand as you do pulls.
Shrug and tighten your arms first to feel excessive tension, then relax and focus on feeling the band stretch as your shoulders drop and arms extend.
You’ll notice also at the top that the tension will abruptly release and the bar will continue up—this is similar to what you should feel as you finish the pull explosively and start moving under the bar.
When I first started snatching, I used the idea of my arms as rubber bands that stretched as I accelerated up, then at the top under maximal tension, snapped me back down under the bar.
Remember that “relaxed” arms doesn’t mean there’s no tension in them—there will be plenty—you’re holding onto and accelerating a heavy barbell. The idea of relaxing is more to prevent active tension and ensure you’re focused on generating maximal force with the legs and hips, and that force is transmitted to the bar as completely as possible. As Tim Swords says, you’re “towing” the bar.
Even if the arms are slightly bent in a lift, the intent to relax and feel the stretch through them and the traps will improve force transmission and bar acceleration.