Passive, static (5)
I believe the answer is:
This clue is a double definition.
'passive' is the first definition.
(I've seen this before)
'static' is the second definition.
(both can mean not moving)
(Other definitions for inert that I've seen before include "Chem. non-reactive" , "Unmoving" , "Not chemically active" , "Slow and apathetic" , "Disinclined to act" .)