Still locked, editor's holding up a French competition anyone can enter (8)
I believe the answer is:
unopened
'competition anyone can enter' is the definition.
I can't judge whether this defines the answer.
'still locked editor's holding up a french' is the wordplay.
'still' becomes 'open' (I can't explain this - if you can you should give a lot more credence to this answer).
'locked' means one lot of letters goes inside another (I've seen this in other clues).
'editor' becomes 'ed' (abbreviation).
'holding up' is a charade indicator (letters next to each other) (some letters go underneath or hold up others).
'a french' becomes 'un' ('a' in French).
'ed' after 'un' is 'uned'.
'open' placed into 'uned' is 'UNOPENED'.
Can you help me to learn more?
(Other definitions for unopened that I've seen before include "Still closed" , "Remaining closed" , "barred" , "Having held onto seal" , "Remaining sealed" .)