Informal name that means nothing to a sailor? (5)
I believe the answer is:
Here is my best explanation:
'informal name that means nothing to a' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'sailor?' is the wordplay.
I cannot really understand how this works, but
'sailor?' could be 'jack' (I've seen this before) and 'jack' is present in the answer.
A single letter 'o' remains which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Another definition for jacko that I've seen is "- - - -lantern".)