Do nothing, say about a gun being unloaded (8)
I believe the answer is:
stagnate
'do nothing' is the definition.
(thesaurus)
'say about a gun being unloaded' is the wordplay.
'say' becomes 'state' ('state' can be a synonym of 'say'**).
'about' is an insertion indicator.
'being unloaded' suggests removing the centre (the content of the word is unloaded).
'gun' with its middle taken out is 'gn'.
'a'+'gn'='agn'
'state' placed around 'agn' is 'STAGNATE'.
(Other definitions for stagnate that I've seen before include "Become dull through inactivity" , "Become foul (water)" , "Of water, become still and stale" , "Become stale or inactive" , "Be idle" .)