In general, this isn't an easy problem. There are huge differences among fishnets in spacing, thickness, color and regularity of the thread pattern. Different PS techniques are more suited to different types of fishnets. For example, Fourier Transform methods generally are best with wide threads spaced very regularly, and which are slightly OOF, but FFT methods are not optimal for very sharp thin irregularly spaced threads. In contrast a simple (masked) Dust and Scratches filter can do miracles with very thin, irregularly spaced, really well-focused images. Sometimes a combination of techniques is needed.
That being said, don't expect a miracle: You will never "remove" a fishnet using PS. There will always be some remnant of the original pattern. For some uses, no one will ever notice this. For other uses, the remaining pattern will be completely unacceptable.
By far, if at all possible, the best way to "remove a fishnet" is to re-shoot the photo without the model wearing them. If this is a commercial image that you didn't photograph, buy or license a new one where the model isn't wearing fishnets.
The bottom line is that we need to see what you are talking about before we make a recommendation.
Tom M
