Stuff at sea it polluted (7)
I believe the answer is:
satiate
'stuff' is the definition.
('satiate' can be a synonym of 'stuff')
'at sea it polluted' is the wordplay.
'polluted' indicates anagramming the letters.
'at'+'sea'+'it'='atseait'
'atseait' anagrammed gives 'SATIATE'.
(Other definitions for satiate that I've seen before include "Fill to satisfaction" , "stuff" , "Satisfy fully, cloy with excess" , "Overstuff" , "Overfill - gorge" .)