A grand art holding struck by shock (6)
I believe the answer is:
aghast
'holding struck by shock' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'a grand art' is the wordplay.
'a grand' becomes 'ag' (I've seen this in other clues).
'art' becomes 'hast' (I can't explain this - if you can you should give a lot more credence to this answer).
'ag'+'hast'='AGHAST'
Can you help me to learn more?
(Other definitions for aghast that I've seen before include "Horror-struck" , "Stupefied with horror" , "Filled with horror or shock" , "Horror-stricken, filled with consternation" , "Horrified, filled iwth consternation" .)