"I have a simple philosophy: Fill what's empty. Empty what's full. Scratch where it ____” (Alice Roosevelt Longworth) (6)
I believe the answer is:
itches
(Other definitions for itches that I've seen before include "Tingles as skin may" , "causes irritation" , "Has uncomfortable tingling sensation" , "They're in need of a scratch" , "They need to be scratched" .)