Lawman is going back over the woman's fines (7)
I believe the answer is:
sheriff
'lawman' is the definition.
(I know that sheriff is a type of lawman)
'is going back over the woman's fines' is the wordplay.
'going back' says the letters should be written in reverse.
'over' indicates putting letters inside.
'the woman's' becomes 'her' (belonging to a woman).
'fines' becomes 'ff' (an abbreviation for fine written twice).
'is' written backwards gives 'si'.
'si' placed around 'her' is 'sheri'.
'sheri'+'ff'='SHERIFF'
(Other definitions for sheriff that I've seen before include "Lawman of the wild west" , "Local officer" , "Chief officer of the Crown in a county" , "Scottish judge" , "Scots judge" .)