Loafer is riled badly (5)
I believe the answer is:
idler
'loafer' is the definition.
(I know that loafer can be written as idler)
'riled badly' is the wordplay.
'badly' is an anagram indicator (letters in the wrong order).
'riled' is an anagram of 'IDLER'.
'is' acts as a link.
(Other definitions for idler that I've seen before include "Person who does no work" , "Lazybones; gear wheel" , "Slacker" , "One resting" , "Johnson's work" .)