Clean, not all water in sewer! (5)
I believe the answer is:
rinse
'clean' is the definition.
(I've seen this in another clue)
'not all water in sewer' is the wordplay.
'not all' says the answer is hidden in the clue (only some of the letters).
'RINSE' can be found hidden inside 'water in sewer'.
(Other definitions for rinse that I've seen before include "Sluice" , "Wash in clean water" , "Hair colourant" , "Use water to remove soap" , "Wash - siren (anag)" .)