Is it, for some obscure reason, not to be revealed? (4,6)
I believe the answer is:
dark secret
'reason not to be revealed?' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'is it for some obscure' is the wordplay.
'is it' becomes 'secret' (I can't explain this - if you can you should believe this answer much more).
'for' says to put letters next to each other (I've seen this in other clues).
'some obscure' becomes 'dark' (I've seen this in another clue).
'secret' put after 'dark' is 'DARK SECRET'.
Can you help me to learn more?
(Another definition for dark secret that I've seen is " something to hide".)