Still upset? Not very (5)
I believe the answer is:
inert
'still' is the definition.
(not moving)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for inert that I've seen before include "Unreactive; still" , "Sluggish, still" , "Not chemically active" , "Slow and apathetic" , "Chem. non-reactive" .)