Wharfs (5)
(Other definitions for piers that I've seen before include "Supports for bridge spans" , "Landing stages" , "Old ploughman" , "Jetties" .)
'wharfs' is the definition.
('dock' can be a synonym of 'wharf')
This is the entire clue.
(Other definitions for docks that I've seen before include "Cuts short; port features" , "Reduces" , "Cuts short - coarse weeds" , "Broadleaved weeds" , "Harbour" .)