Isle with dump and drain cover (7)
I believe the answer is:
manhole
'drain cover' is the definition.
(I've seen this before)
'isle with dump' is the wordplay.
'isle' becomes 'man' (the Isle of Man is an example).
'with' is a charade indicator (letters next to each other).
'dump' becomes 'hole' (hole can mean a dump or unpleasant place).
'man'+'hole'='MANHOLE'
'and' is the link.
(Other definitions for manhole that I've seen before include "Access chamber to sewer or drain" , "restricted opening" , "Street access cover" , "Aperture to sewer, duct etc" , "Inspection chamber" .)