Gun entanglements set up (4)
I believe the answer is:
sten
'gun' is the definition.
(British sub-machine gun)
'entanglements set up' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'set' is 'ste' which is located in the answer.
A single letter 'n' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sten that I've seen before include "British WWII submachine gun" , "name of gun" , "Type of lightweight submachine gun" , "Deadly weapon" , "weaponry" .)