Niche 2 (PA)

I asked for feedback on my niche and the response was to find the industry of my client working in corporate.
I just started my business so I don’t have many clients, and the 2 clients I have work in the publishing industry, actually one recommended me to a friend and that’s how I got the second client as a client.
Would you “use” your client to research about the industry? because I don’t know much about it.
I still have a corporate job full time in the transport industry, very big company but they shut me down when trying to be vocally and help people (even for free) so I’m not considering it.
Thought that publishing would be a good idea as I already have 2 clients in this industry.
What’s your thoughts?