Almost hurt in the empty horror (9)
I believe the answer is:
nightmare
'horror' is the definition.
(I've seen this before)
'almost hurt in the empty' is the wordplay.
'almost' becomes 'nigh' (nigh can mean almost or nearly).
'hurt' becomes 'mar' (both can mean to harm).
'in' is an insertion indicator.
'empty' says to hollow out the word (remove centre letters).
'the' with its middle taken out is 'te'.
'mar' put within 'te' is 'tmare'.
'nigh'+'tmare'='NIGHTMARE'
(Other definitions for nightmare that I've seen before include "Scary nocturnal fantasy" , "that might upset the rest" , "Awful experience" , "Bad dream" , "Frightening dream" .)