Drain off lowest part (5)
I believe the answer is:
nadir
'lowest part' is the definition.
The answer and definition can be both locations as well as being singular nouns.
Maybe there's a link between them I don't understand?
'drain off' is the wordplay.
'off' is an anagram indicator.
'drain' anagrammed gives 'NADIR'.
Can you help me to learn more?
(Other definitions for nadir that I've seen before include "Lowest point, or time of deepest depression." , "Drain (anag)" , "extremely low position" , "deep despair" , "Rock bottom" .)