I think all effects in practice are indirect, but “direct” can be used to mean a causal effect about which we have direct evidence, i.e. we made observations about the cause on the outcome without need for discussing intermediate outcomes, not from piecing multiple steps of causal effects together in a chain. The longer the causal chain, the more likely there are to be effects in the opposite direction along parallel chains. Furthermore, we should generally be skeptical of any causal claim, so the longer the causal chain, the more claims of which we should be skeptical, and the weaker we should expect the overall effect.
I think all effects in practice are indirect, but “direct” can be used to mean a causal effect about which we have direct evidence, i.e. we made observations about the cause on the outcome without need for discussing intermediate outcomes, not from piecing multiple steps of causal effects together in a chain. The longer the causal chain, the more likely there are to be effects in the opposite direction along parallel chains. Furthermore, we should generally be skeptical of any causal claim, so the longer the causal chain, the more claims of which we should be skeptical, and the weaker we should expect the overall effect.