Watch the Searching for Clues online guitar lesson by Jon Finn from 30 Melodic Modal Rock Licks You MUST Know
This lick starts with a series of small arpeggios that outline the sound of the chords being played. Immediately after, it goes straight to a passage that outlines the A Mixolydian scale sound.
Check the notation and tablature to get the finer details. Practice with the backing track, then invent your own version of this lick!