Infected for a month with nervous disorder (6)
I believe the answer is:
septic
'infected' is the definition.
(I know that infected can be written as septic)
'a month with nervous disorder' is the wordplay.
'a month' becomes 'Sept' (Sept is an example).
'with nervous disorder' becomes 'ic' (I can't justify this - if you can you should believe this answer much more).
'sept'+'ic'='SEPTIC'
'for' is the link.
Can you help me to learn more?
(Other definitions for septic that I've seen before include "Contaminated with disease-causing bacteria" , "Caused by putrefaction" , "Putrefactive" , "Poisoned" , "Putrid" .)