### Clue: Ruth Rendell's first English detective (7)
### Answer: REMORSE 
 ### Explanation: Definition: Ruth
  R(*first* letter of *Rendell*) + E(*$$E$$nglish*) + MORSE(Detective Chief Inspector, *detective* in Colin Dexter's series of novels set in Oxford.  Among other things, Endeavour – his first name -was a cryptic crossword enthusiast).
Defn:  The noun meaning compassion,contrition,remorse, the root of the more common "*ruth*less".  Probably some connection (but I don't know what) with Ruth, the biblical character known for her kindness and faithfulness.  Nice surface to this as Ruth Rendell has her own series of mystery novels, centred around another English detective.