Wartime menace about to be destroyed (1-4)
I believe the answer is:
u-boat
'wartime menace' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'about to be destroyed' is the wordplay.
'to be destroyed' is an anagram indicator.
'about' with letters rearranged gives 'U-BOAT'.
Can you help me to learn more?
(Other definitions for u-boat that I've seen before include "German wartime submarine" , "Submersible warship armed with torpedoes" , "About (anag)" , "German submarine of WW2" , "German World War One or World War Two submarine" .)