Ghastly horse going without its carriage? (7)
I believe the answer is:
macabre
'ghastly' is the definition.
(I know that ghastly can be written as macabre)
'horse going without its carriage?' is the wordplay.
I cannot quite see how this works, but
'carriage?' could be 'cab' (cab is a kind of carriage) and 'cab' is found in the answer.
'horse' could be 'mare' (mare is a kind of horse) and 'mare' is present in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for macabre that I've seen before include "Morbidly repellent" , "Ghastly, gruesome" , "Grotesque" , "'Grim, repellent (7)'" , "Brace ma, being gruesome" .)