Writer leaves maneater in locked passage (5)
I believe the answer is:
canal
'locked passage' is the definition.
(canals have locks)
'writer leaves maneater' is the wordplay.
'writer' becomes 'nib' (something which writes).
'leaves' is a deletion indicator.
'maneater' becomes 'cannibal'.
'cannibal' with 'nib' taken out is 'CANAL'.
'in' acts as a link.
(Other definitions for canal that I've seen before include "Duct" , "Grand Union perhaps" , "Man-made strip of water" , "Artificial waterway as at Panama (5)" , "Long, narrow strip of water" .)