Don’t forget to say which part of a sentence confuses you :p Guessing, like Con-gras-tue-les-chiens, that it’s là …

This là is demonstrative in origin, used to indicate "this here" or "that one there", which is where Aerovistae’s translation comes into play. It suggests the speaker either looking at or actively discussing a particular métier, and then issuing this opinion. We could be passing by a stock brokerage or something, both glance up at the sign, and you say the sentence you quoted.

Also, demonstratives imply a focus and the focus implies an exclusion of other things. So say I’m talking about honest métiers with you. You jokingly suggest the profession of pickpocket. I could reply with the sentence you quoted, meaning, "No, not that one. Back to the ones I meant!"

That function of focus has, over time, generalized so that là doesn’t necessarily need an obvious referent but can just mean "here, now, whatever is happening", as in the Collins entry:

Non, là, je ne vois vraiment pas ce qu’on peut faire. No, I really can’t see what we can do about this.

Là il exagère! Now he’s really going too far!

This is probably the sense intended since the more narrowly demonstrative sense would tend to be expressed as « ce métier-là ».