Are working in companies producing munitions (8)
I believe the answer is:
firearms
'munitions' is the definition.
(firearm is a kind of munition)
'are working in companies' is the wordplay.
'working' indicates anagramming the letters.
'in' indicates putting letters inside.
'companies' becomes 'firms' (I've seen this before).
'are' is an anagram of 'ear'.
'ear' placed into 'firms' is 'FIREARMS'.
'producing' is the link.
(Other definitions for firearms that I've seen before include "Rifles, guns, pistols etc" , "Weapons" , "they can kill people" , "Portable guns" , "Weaponry" .)