Turn out a lunatic marine (8)
I believe the answer is:
nautical
'marine' is the definition.
(I know this)
'turn out a lunatic' is the wordplay.
'turn out' indicates anagramming the letters.
'a'+'lunatic'='alunatic'
'alunatic' is an anagram of 'NAUTICAL'.
(Other definitions for nautical that I've seen before include "Like 8 21[HORATIO NELSON]" , "Marine" , "Concerning sailors" , "Relating to sailors" , "about boats" .)