Current breaking through wharf (4)
I believe the answer is:
pier
'wharf' is the definition.
(I've seen this before)
'current breaking through' is the wordplay.
'current' becomes 'I' (symbol for electric current).
'breaking' indicates putting letters inside.
'through' becomes 'per' (I've seen this in another clue).
'i' put into 'per' is 'PIER'.
(Other definitions for pier that I've seen before include "Structure extending seawards" , "Ripe as a jetty (4)" , "Seaside structure" , "Landing-stage or promenade" , "Structure with a deck, built over water" .)