Nautical ode turned out to be instructive (11)
I believe the answer is:
educational
'to be instructive' is the definition.
('educational' can be similar in meaning to 'instructive')
'nautical ode turned' is the wordplay.
'turned' indicates anagramming the letters.
'nautical'+'ode'='nauticalode'
'nauticalode' is an anagram of 'EDUCATIONAL'.
'out' acts as a link.
(Other definitions for educational that I've seen before include "Relating to teaching" , "Providing knowledge" , "A docile aunt (anag) - instructive" , "as an aid to learning" , "Academic" .)