Wine after month in effect contaminated (8)
I believe the answer is:
doctored
'contaminated' is the definition.
(I've seen this before)
'wine after month in effect' is the wordplay.
'wine' becomes 'red' (red wine is an example).
'after' means one lot of letters go next to another.
'month' becomes 'oct' (abbreviation for October).
'in' indicates putting letters inside.
'effect' becomes 'do' (synonyms).
'oct' going within 'do' is 'docto'.
'red' put after 'docto' is 'DOCTORED'.
(Other definitions for doctored that I've seen before include "Contaminated" , "Patched up or falsified - like medical man?" , "Adulterated" .)