Answer:
Servitude is the state of being a slave. The clues to deduce it are "reduced to", "under the harness" and "drudgery of cities."
Step-by-step explanation:
To serve is the action where someone or in this case the horse has to follow the commands of someone else, then we have the clue words "reduced" which shows that he has lost the independent value he had, "under the harness" shows him as a prisoner, and the "drudgery" talks about a hard life of intense work in a stressing place,