Citadel without key or lock (5)
I believe the answer is:
tress
'lock' is the definition.
(both can mean a piece of hair)
I can't explain the rest of the clue.
(Other definitions for tress that I've seen before include "Switch" , "Obsolete support" , "Bit of hair" , "Long lock or plait of hair" , "Rests (anag.)" .)