A month in charge and it's infected (6)
I believe the answer is:
septic
'infected' is the definition.
(I know that infected can be written as septic)
'a month in charge and it's' is the wordplay.
'a month' becomes 'sep' (abbreviation for September).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'and' is a charade indicator (letters next to each other).
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'ic' put after 't' is 'tic'.
'sep'+'tic'='SEPTIC'
(Other definitions for septic that I've seen before include "Contaminated with disease-causing bacteria" , "Of wound, infected with pus" , "Poisonous" , "Infected with bacteria" , "Of wound, filled with pus" .)