Ill-fated ratbags nailed fences (8)
I believe the answer is:
accursed
'ill-fated' is the definition.
(I've seen this in another clue)
'ratbags nailed fences' is the wordplay.
'ratbags' becomes 'curs' (I can't explain this - if you can you should give a lot more credence to this answer).
'nailed' becomes 'aced' (acing is a kind of nailing).
'fences' is an insertion indicator (inserted letters are fenced off).
'curs' placed into 'aced' is 'ACCURSED'.
Can you help me to learn more?
(Other definitions for accursed that I've seen before include "Detestable (colloq.)" , "Cue cards (anag) - doomed" , "Damned" , "Goddamn" , "Wretched" .)