Chief magistrate once concerned with first woman (5)
I believe the answer is:
reeve
'chief magistrate' is the definition.
'reeve' can be an answer for 'magistrate' (type of historical legal official). I am not sure about the 'chief' bit.
'once concerned with first woman' is the wordplay.
'once concerned' becomes 're' (I can't explain this - if you can you should give a lot more credence to this answer).
'with' means one lot of letters go next to another.
'first woman' becomes 'Eve' (first woman in the bible).
're'+'eve'='REEVE'
Can you help me to learn more?
(Other definitions for reeve that I've seen before include "sort of ruff" , "Comic actor" , "Former magistrate" , "old-fashioned official" , "Historical magistrate" .)