Answer:
What indulgence mean in this sentence from the passage is "willingness to be lenient rather than strict"
Step-by-step explanation:
The word Indulgence means remission of the punishment totally or partially for the incorrect actions, then from the complete excerpt "I wondered often what my master saw to admire so much in the sullen boy, who never, to my recollection, repaid his indulgence by any sign of gratitude." they are talking about being indulgent with a little boy that means giving the kid permission to do as he wishes.