Mutinous aboard U-boat, possibly with rationed supply (13)
I believe the answer is:
insubordinate
'mutinous' is the definition.
(similar in meaning)
'aboard u-boat possibly with rationed supply' is the wordplay.
'aboard' becomes 'in' (eg in a vehicle).
'u-boat' becomes 'sub' (German submarine).
'possibly with rationed supply' becomes 'ordinate' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in'+'sub'+'ordinate'='INSUBORDINATE'
Can you help me to learn more?
(Other definitions for insubordinate that I've seen before include "Recalcitrant" , "Mutinous" , "Cheeky" , "Not submissive to authority" , "Badly behaved" .)