Canal features may be security devices (5)
I believe the answer is:
locks
I believe this is a double definition.
'canal features' is the first definition.
(I've seen this before)
'security devices' is the second definition.
(I've seen this in another clue)
'may be' acts as a link.
(Other definitions for locks that I've seen before include "Secure fasteners for doors" , "Tresses" , "Clusters of hair" , "Canal features" , "Fastens - hair" .)