Water container covered in kind of green waste (8)
I believe the answer is:
sewerage
'waste' is the definition.
(I know that sewerage is a type of waste)
'water container covered in kind of green' is the wordplay.
'water container' becomes 'ewer' (I've seen this in another clue).
'covered in' means one lot of letters goes inside another.
'kind of green' becomes 'sage'.
'ewer' going inside 'sage' is 'SEWERAGE'.
(Other definitions for sewerage that I've seen before include "Provision of drainage" , "System of drains to carry away waste" , "removal of waste matter" , "waste products" , "For removal of surplus water" .)