Appeal involving trade union overturned and excluded (7*)
I believe the answer is:
Here is my best explanation:
'appeal' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe there's a link between them I don't understand?
'involving trade union overturned and excluded' is the wordplay.
'involving trade' becomes 'sh' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'union' becomes 'tu' (I've seen this in other clues).
'overturned' shows that the letters should be reversed in order.
'and' means one lot of letters go next to another.
'excluded' becomes 'out' (I've seen this before).
'tu' in reverse letter order is 'ut'.
(Other definitions for shutout that I've seen before include "Prevent from entering" and "Excluded".)