Loafer gets terribly riled (5)
I believe the answer is:
idler
'loafer' is the definition.
(I know that loafer can be written as idler)
'terribly riled' is the wordplay.
'terribly' indicates an anagram.
'riled' with letters rearranged gives 'IDLER'.
'gets' acts as a link.
(Other definitions for idler that I've seen before include "Couch potato" , "Laggard" , "Reluctant worker" , "A lazy loafer" , "Slacker" .)