Drain burst in lowest level (5)
I believe the answer is:
nadir
'lowest level' is the definition.
(thesaurus)
'drain burst' is the wordplay.
'burst' is an anagram indicator.
'drain' with letters rearranged gives 'NADIR'.
'in' acts as a link.
(Other definitions for nadir that I've seen before include "You can't sink lower!" , "Lowest point, or time of deepest depression." , "most unsuccessful point" , "It's the depths" , "Rock bottom" .)