Literary work, after only half a month, upset everyone (7)
I believe the answer is:
novella
'literary work' is the definition.
(novella is a kind of literary work)
'month upset everyone' is the wordplay.
'month' becomes 'nove' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'upset' is a reversal indicator.
'everyone' becomes 'all' (all people).
'all' in reverse letter order is 'lla'.
'nove'+'lla'='NOVELLA'
'after only half a' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for novella that I've seen before include "Small book" , "Slim work of fiction" , "Long short story?" , "short book" , "Slim volume of fiction" .)