Horrified at being cut by jagged gash (6)
I believe the answer is:
aghast
'horrified' is the definition.
(I know that horrified can be written as aghast)
'being cut by jagged gash' is the wordplay.
I cannot quite see how this works, but
an anagram of 'gash' is 'ghas' which is within the answer.
'by' could be 'at' and 'at' is located in the remaining letters.
No letters remain.
This explanation may well be incorrect...
'at' is the link.
Can you help me to learn more?
(Other definitions for aghast that I've seen before include "Filled with terror" , "Filled with fear or horror" , "Horror-struck" , "Stunned" , "Horrified, filled iwth consternation" .)