Riled slovenly slacker (5)
I believe the answer is:
idler
'slacker' is the definition.
(I've seen this before)
'riled slovenly' is the wordplay.
'slovenly' is an anagram indicator.
'riled' is an anagram of 'IDLER'.
(Other definitions for idler that I've seen before include "Bummer" , "Johnson's work" , "Lazybones; gear wheel" , "papers" , "Do-nothing" .)