Ghastly, frightful (8)
I believe the answer is:
horrible
I believe this clue is a double definition.
'ghastly' is the first definition.
(I've seen this before)
'frightful' is the second definition.
(synonyms)
(Other definitions for horrible that I've seen before include "Atrocious" , "Beastly" , "Dreadful, awful" , "Unkind" , "'Ghastly, grisly (8)'" .)