I know it's part of the trinity but with it being close to Lewisville is the fish in that part of the river ok to eat or is it unsafe from any part of the trinity?

That area is way above the problems. The advisory is caused by the Aerospace companies in the DFW metroplex. Eat away.

Clear Fork of Trinity River from Benbrook Reservoir dam and West Fork from Lake Worth dam, including main stem of the Trinity downstream to US 287 bridge. Portions of Anderson, Dallas, Ellis, Freestone, Henderson, Kaufman, Navarro and Tarrant counties.
Chemicals of Concern: Polychlorinated biphenyls (PCBs), Dioxins

One of the 6 Dallas city water intakes is about a mile up from McCinnish park landing. About 7 miles above that is a waste water treatment. Go figure.

In general Dams are good filters. Stuff either sinks or floats in water, and many dam draws from the middle of the water column (usually). There are exceptions to this, where the lakes only have a spillway.

I have eaten fish from that stretch more than once, and other than my twitch, I am still alright.