Disobedient aboard sinking boat, one triad destroyed (13)
I believe the answer is:
insubordinate
'disobedient' is the definition.
(similar in meaning)
'aboard sinking boat one triad destroyed' is the wordplay.
'aboard' becomes 'in' (I've seen this in other clues).
'sinking boat' becomes 'sub' (submarine - boat which sinks below the sea).
'destroyed' indicates an anagram.
'one'+'triad'='onetriad'
'onetriad' with letters rearranged gives 'ordinate'.
'in'+'sub'+'ordinate'='INSUBORDINATE'
(Other definitions for insubordinate that I've seen before include "Recalcitrant" , "Not submissive to authority" , "Disobedient" , "Insolent" , "undisciplined" .)