Mat originally straightened, dragged through the mud (8)
I believe the answer is:
maligned
'dragged through the mud' is the definition.
('malign' can be a synonym of 'drag through the mud')
'mat originally straightened' is the wordplay.
'originally' suggests taking the first letters.
'straightened' becomes 'aligned' (I've seen this in another clue).
The first letter of 'mat' is 'm'.
'm'+'aligned'='MALIGNED'
(Other definitions for maligned that I've seen before include "stigmatised" , "Vilified" , "Abused" , "Unjustly slandered" , "Defamed" .)