Deepest point in broken drain (5)
I believe the answer is:
nadir
'deepest point' is the definition.
(I've seen this before)
'broken drain' is the wordplay.
'broken' indicates anagramming the letters.
'drain' is an anagram of 'NADIR'.
'in' acts as a link.
(Other definitions for nadir that I've seen before include "Low-water mark" , "All-time low" , "deep despair" , "Given lowest place" , "Floor of drain in need of repair" .)