You wouldn't normally say "reduce backlog". You would say "reduce the backlog" Taxes were due in April and we still have 50 returns not filed. Are you going to hire someone to help reduce the backlog? We have a backlog of unfulfilled orders. Let's get those shipped before we start getting a reputation for being unreliable. I think John overstated the implication that a backlog means new work is being delayed. That would be a possibility but is not implicit in the word. "Our highest profit margins are in doing commercial inspections and that business is the most important. Let's not worry too much about the backlog in our residential orders"

A backlog usually means that the business is “behind” in responding to or fulfilling orders or in finishing work. In other words, there is a lot of “old” business still to be done, and so the company cannot immediately take care of “new” business; the new work gets delayed until the old work gets done. This often happens because the company is very busy, or because it has encountered some kind of problem that delays it getting things done on time. To reduce backlog means to do something to get the old work done, so that the new work can be dealt with with less of a delay.