Report of low reef in wharf (4)
I believe the answer is:
quay
'wharf' is the definition.
(I know that wharf can be written as quay)
'report of low reef' is the wordplay.
'report of' indicates a 'sounds like' (homophone) clue.
'low reef' becomes 'cay' (I've seen this in another clue).
'cay' is a homophone of 'QUAY'.
'in' acts as a link.
(Other definitions for quay that I've seen before include "Dock's loading area" , "Dock, wharf" , "Pier" , "Landing place" , "crucial, by the sound of it" .)