Part of drainage system not good state (5)
I believe the answer is:
utter
'state' is the definition.
(both can mean to say)
'part of drainage system not good' is the wordplay.
'part of drainage system' becomes 'gutter'.
'not' is a deletion indicator.
'good' becomes 'g' (abbreviation).
'gutter' with 'g' taken away is 'UTTER'.
(Other definitions for utter that I've seen before include "outright" , "Speak - out-and-out" , "issue" , "State - unqualified - rank" , "Absolute - state" .)