Author wrong to delete conclusion (4)
I believe the answer is:
amis
'author' is the definition.
(Kingsley or Martin Amis)
'wrong to delete conclusion' is the wordplay.
'wrong' becomes 'mis' (similar in meaning).
'to' says to put letters next to each other (I've seen this in other clues).
'delete conclusion' becomes 'a' (I can't explain this - if you can you should give a lot more credence to this answer).
'mis' after 'a' is 'AMIS'.
Can you help me to learn more?
(Other definitions for amis that I've seen before include "Kingsley, Martin or John" , "Author Kingsley or Martin" , "Author of Lucky Jim, d.1995" , "English writer" , "Kingsley -, English author (Lucky Jim)" .)