Give ground on the subject of indulgence (7)
I believe the answer is:
retreat
'give ground' is the definition.
'on the subject of indulgence' is the wordplay.
'on' is a charade indicator (letters next to each other).
'the subject of' becomes 're' (I've seen this in other clues).
'indulgence' becomes 'treat' (I've seen this before).
're' put next to 'treat' is 'RETREAT'.
(Other definitions for retreat that I've seen before include "Climb down" , "Take flight" , "Pull back" , "Back away" , "concession" .)