Metal jacket of interrogator being worn (4)
I believe the answer is:
iron
'metal' is the definition.
(iron is a metal)
'jacket of interrogator being worn' is the wordplay.
'jacket of interrogator' becomes 'ir' (I am not sure about this - if you are sure you should believe this answer much more).
'being worn' becomes 'on'.
'ir'+'on'='IRON'
Can you help me to learn more?
(Other definitions for iron that I've seen before include "The one who was 'not for turning'" , "The metallic element plays a role in the transport of oxygen by the blood" , "What's used to make pitch" , "Smooth (clothes)" , "Club to smooth the cloth" .)