Wiktionary
subindustry
n. An industry that makes up part of a larger industry.
Usage examples of "subindustry".
As mentioned earlier, there was so much kidnapping for hire in the late 1920s and early 1930s that a subindustry grew up in laundering ransom money.
A stupid idea, yes, but it had not only caught on, but spawned a whole range of subindustries to support and complement it.