Please help with "bird's nest" -like print failure

[Roberts_Clif]

I think this may be what I've read about people calling "under-extrusion"? Is that true?
What might some possible causes be, and steps that I could take to remedy them?

Under Extrusion YES.
Possible causes

1. Teflon tube deformed / burnt.
2. Slicer configuration error. "I did this somehow configured 3 mm filament when using 1.75mm filament.
Photo Below. Fish should be solid not fishnet


3mm - 1.75mm.jpg