Unmannerly chit initially having fling with one’s husband (8)
I believe the answer is:
churlish
'unmannerly' is the definition.
'chit initially having fling with one's husband' is the wordplay.
'initially' suggests taking the first letters.
'having' means one lot of letters go next to another.
'fling with' becomes 'hurl' (I've seen this before. I am not sure about the 'with' bit.).
'one's' becomes 'is' (roman numeral).
'husband' becomes 'h'.
The first letter of 'chit' is 'c'.
'c'+'hurl'+'is'+'h'='CHURLISH'
(Other definitions for churlish that I've seen before include "Rude and surly" , "Uncouth" , "Rude and boorish" , "Ill-mannered and surly" , "Mean-spirited and surly" .)