Wreck site visit, reportedly, with plot (6)
I believe the answer is:
seabed
'wreck site' is the definition.
(where there are shipwrecks)
'visit reportedly with plot' is the wordplay.
'visit' becomes 'see' (seeing is a kind of visiting).
'reportedly' shows a homophone (sound like).
'with' says to put letters next to each other.
'plot' becomes 'bed' (a plot of land).
'see' sounds like 'sea'.
'sea'+'bed'='SEABED'
(Other definitions for seabed that I've seen before include "Debase (anag)" , "Davy Jones's locker" , "marine base" , "The ocean floor, not for sleeping" , "Bottom of the ocean" .)