Shocks or reprocessed accretion as the source of TDE optical light
In plain words
Tidal disruption flares glow in visible light from a region much larger than the expected disk of infalling gas. That light could come from colliding streams of star debris or from a gas cloud that absorbs and re-emits light from the disk.
Precise statement
Optical and UV emission of TDEs is roughly blackbody with $T \sim 2e4 \text{ to } 4e4\,\mathrm{K}$ and $\mathrm{radius} \sim 1e14 \text{ to } 1e15\,\mathrm{cm}$, much larger than the circularization radius. Determine whether it is powered by shocks where the debris stream intersects itself (Piran et al. 2015) or by reprocessing of accretion luminosity in an optically thick envelope or outflow, using light-curve shapes, line profiles and X-ray to optical ratios.
What would settle it
Radiation hydrodynamics simulations of disruption, circularization and emission that reproduce observed temperatures, radii and line profiles for realistic black-hole masses.