For clear soup, the broth needs to be exceptionally clear and free of sediment. For a stew base, clarity is less critical, and a slightly cloudy broth is perfectly acceptable and often adds richness.
The primary difference lies in the intended presentation and flavor profile. When serving a clear soup, such as consommé or a light chicken broth, visual appeal is paramount. The broth should be translucent, allowing you to see through it clearly. This requires careful skimming during simmering to remove impurities and potentially straining through cheesecloth or a fine-mesh sieve.
In contrast, a broth used as a stew base is more about flavor contribution than visual perfection. The other ingredients in the stew will contribute their own textures and colors, so a slightly cloudy broth won't detract from the final dish. In fact, the cloudiness often comes from dissolved proteins and fats, which can enhance the stew's richness and body. A cloudy broth indicates that more flavor compounds have been extracted from the bones and vegetables, which is generally desirable in a stew. Therefore, while you still want to avoid excessive sediment or large particles, striving for crystal-clear broth is unnecessary and can even be detrimental to the stew's overall flavor.
If you accidentally end up with a cloudy broth for clear soup, try using an egg white raft clarification method. Gently simmer the broth with beaten egg whites; they will coagulate and trap impurities, allowing you to strain out a perfectly clear broth.