Warship about to explode (1-4)
I believe the answer is:
u-boat
'warship' is the definition.
(U-boat is an example)
'about to explode' is the wordplay.
'to explode' indicates anagramming the letters.
'about' with letters rearranged gives 'U-BOAT'.
(Other definitions for u-boat that I've seen before include "Take pool exercise" , "Sea vessel" , "German submarine of WW2" , "Submersible warship armed with torpedoes" , "German WW 2 sub" .)