Lock down leader abandoning state (5)
I believe the answer is:
tress
'lock down' is the definition.
(lock of hair which hangs down)
'leader abandoning state' is the wordplay.
'leader abandoning' means to remove the first letter.
'state' becomes 'stress' (to stress is to state with emphasis).
'stress' with its first letter taken off is 'TRESS'.
(Other definitions for tress that I've seen before include "Rests (anag.)" , "Long piece of hair" , "Obsolete support" , "Braid of hair" , "Switch" .)