Idleness (8)
'idleness' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for inaction that I've seen before include "Ionic tan (anag.)" , "Idleness of nicotian sort" , "doing nothing whatsoever" , "This is not working" , "Lethargy -- not in CIA (anag)" .)
'idleness' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for inertia that I've seen before include "Passiveness" , "showing reluctance to move" , "A disposition to remain inactive" , "Disinclination to act" , "Apathetic state" .)