See turning in the gun that was misappropriated (6)
I believe the answer is:
stolen
'misappropriated' is the definition.
(I've seen this before)
'see turning in the gun' is the wordplay.
'see' becomes 'lo' (archaic exclamation meaning 'look!').
'turning' says the letters should be written backwards.
'in the' means one lot of letters goes inside another.
'gun' becomes 'sten' (British sub-machine gun).
'lo' backwards is 'ol'.
'ol' going into 'sten' is 'STOLEN'.
'that was' acts as a link.
(Other definitions for stolen that I've seen before include "Misappropriated; hot" , "Filched" , "Pinched" , "Purloined or embezzled" , "Purloined in Solent" .)