The image is a bit blurry, but the clownfish seems to look fine. I presume the clownfish is swimming vertically against the wall a lot? That is very normal with clownfish.
What you need to look for with clownfish are:
- If they have trouble swimming. Not like their typical bobbing up and down, actual difficulties swimming.
- Spots or blotches that looks weird on the fish.
- Heavy breathing.
- Damaged fins/etc.
- Being chased relentless by other fish.
That is not an exhaustive list, but generally, if they are doing anything else they are just being clowns. My ocellaris sleeps sideways against the surface of the water at the back of the tank at night. My other one sleeps vertically against the wall. Initially it also swims against the wall during the day.
Clownfish behaviour can also change, especially in our aquarium. They seem to be pretty happy to ditch habits at any point in time, just clowns being clowns.