Unfortunate scrap defended by jerk (6)
I believe the answer is:
tragic
'unfortunate' is the definition.
(I've seen this before)
'scrap defended by jerk' is the wordplay.
'scrap' becomes 'rag' (I've seen this in other clues).
'defended by' is an insertion indicator.
'jerk' becomes 'tic' (jerking movement by the body).
'rag' going into 'tic' is 'TRAGIC'.
(Other definitions for tragic that I've seen before include "Calamitous, very sad" , "Heart-rending" , "Terribly sad and distressing" , "Dire" , "Disastrous, appalling" .)