Vessel restricted, contrarily packed with oxygen (1-4)
I believe the answer is:
u-boat
'vessel' is the definition.
(I've seen this before)
'restricted contrarily packed with oxygen' is the wordplay.
'restricted' becomes 'tabu' (alternative spelling of taboo).
'contrarily' is a reversal indicator (letters in the opposite or contrary direction).
'packed with' is an insertion indicator.
'oxygen' becomes 'O' (atomic symbol for oxygen).
'tabu' reversed gives 'ubat'.
'ubat' enclosing 'o' is 'U-BOAT'.
(Other definitions for u-boat that I've seen before include "Submersible warship armed with torpedoes" , "Sea vessel" , "German wartime submarine" , "Submersible warship of WWII" , "Take pool exercise" .)