Repair service lawyer fronts (4)
I believe the answer is:
darn
'repair' is the definition.
(I know that darn is a more specific form of repair)
'service lawyer fronts' is the wordplay.
'service' becomes 'RN' (abbreviation for Royal Navy).
'lawyer' becomes 'da' (abbreviation for District Attorney).
'fronts' is a charade indicator (letters next to each other).
'rn' put after 'da' is 'DARN'.
(Other definitions for darn that I've seen before include "curse" , "Mend by stitching - damn!" , "Mend (knitted material)" , "Repair by sewing, socks perhaps" , "Mend (woollens)" .)