Drunk wife straddled horse? On the contrary (6)
I believe the answer is:
stewed
'drunk' is the definition.
(I've seen this before)
'wife straddled horse? on the contrary' is the wordplay.
'wife' becomes 'w'.
'straddled horse?' becomes 'deets' (I am not sure about this - if you are sure you should believe this answer much more).
'on' means one lot of letters goes inside another (as in clothing 'on' a person).
'the contrary' says the letters should be written in reverse.
'w' inserted inside 'deets' is 'dewets'.
'dewets' back-to-front is 'STEWED'.
(Other definitions for stewed that I've seen before include "Of tea, left brewing too long" , "felt uneasy" , "Of tea, infused too long" , "Was long embarrassed" , "mortal" .)