Floor of drain in need of repair (5)
I believe the answer is:
nadir
'floor of drain in need of repair' is the definition.
(I've seen this before)
'drain in need of repair' is the wordplay.
'in need of repair' indicates an anagram.
'drain' with letters rearranged gives 'NADIR'.
(Other definitions for nadir that I've seen before include "Lower one cannot get!" , "You can't sink lower!" , "Low spot" , "Low point" , "businessman formerly escaping justice" .)