Morass was sorted out by legislator (5)
I believe the answer is:
swamp
'morass' is the definition.
(thesaurus)
'was sorted out by legislator' is the wordplay.
'sorted out' indicates an anagram.
'by' means one lot of letters go next to another.
'legislator' becomes 'MP' (an MP legislates in parliament).
'was' with letters rearranged gives 'swa'.
'swa'+'mp'='SWAMP'
(Other definitions for swamp that I've seen before include "Boggy area" , "Marshy land" , "Overwhelm; wetland" , "Seasonally flooded low land" , "In flood" .)