A crane turned out to be hidden (6)
I believe the answer is:
arcane
'to be hidden' is the definition.
(I've seen this in another clue)
'a crane turned' is the wordplay.
'turned' indicates an anagram.
'crane' with letters rearranged gives 'rcane'.
'a'+'rcane'='ARCANE'
'out' is the link.
(Other definitions for arcane that I've seen before include "Recondite" , "Mysteriouss or secret" , "Abstruse, mysterious" , "deep" , "Requiring secret or mysterious knowledge" .)