Graciously departs in old cab by Cambs cathedral (10)
I believe the answer is:
handsomely
'graciously' is the definition.
(thesaurus)
'departs in old cab by cambs cathedral' is the wordplay.
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'in' indicates putting letters inside.
'old cab' becomes 'hansom'.
'by' is a charade indicator (letters next to each other).
'cambs cathedral' becomes 'ely' (I've seen this before).
'd' placed within 'hansom' is 'handsom'.
'handsom'+'ely'='HANDSOMELY'
(Another definition for handsomely that I've seen is " Amply, generously".)