Wife engaging in extreme bad language (8)
I believe the answer is:
swearing
'bad language' is the definition.
(I've seen this before)
'wife engaging in extreme' is the wordplay.
'wife' becomes 'w' (abbreviation).
'engaging in' means one lot of letters goes inside another (I've seen this in other clues).
'extreme' becomes 'searing' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'w' inserted into 'searing' is 'SWEARING'.
Can you help me to learn more?
(Other definitions for swearing that I've seen before include "Expressing annoyance" , "promising" , "Taking an oath" , "Affirming or cursing" , "Foul language" .)