Chemically inactive (5)
I believe the answer is:
inert
'chemically inactive' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for inert that I've seen before include "Incapable of acting, like some gas" , "Sluggish - unresponsive" , "Like e.g. xenon" , "Chemically unreactive" , "Sluggish, inactive" .)