Dismal filth abridged (4)
I believe the answer is:
grim
'dismal' is the definition.
(I know that dismal can be written as grim)
'filth abridged' is the wordplay.
'filth' becomes 'grime' (synonyms).
'abridged' means to remove the last letter.
'grime' with its last letter removed is 'GRIM'.
(Other definitions for grim that I've seen before include "Serious; dour" , "Frightful" , "Unrelentingly harsh" , "Severe; horrible" , "The - Reaper is death" .)