Rubbish left in large one, ultimately (5)
I believe the answer is:
bilge
'rubbish' is the definition.
(thesaurus)
'left in large one ultimately' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in' is an insertion indicator.
'large' becomes 'big' ('big' can be a synonym of 'large').
'one ultimately' becomes 'e' (I can't justify this - if you can you should believe this answer much more).
'l' going into 'big' is 'bilg'.
'bilg'+'e'='BILGE'
Can you help me to learn more?
(Other definitions for bilge that I've seen before include "Hogwash" , "(Water at) bottom of ship" , "Lower part of hull; nonsense" , "Rubbish - water in boat" , "Very long film, book etc" .)