Clamped fins is a condition in which the fish will continually hold its fins against its body unless it needs to move. This is not a specific sign of a given infection but is however a symptom that is highly noted to be related to poor water quality within the fish's tank. To make sure that the fish has clamped fins and is not sleeping or resting, try checking in the middle of the day when the lights have been on for a while. If you check right after the lights are been turned on or off the fish could be still sleeping, or getting used to the bright lights as it awakens from the bright lights.
The only symptoms of this include the fish staying in one spot for periods, having all of its fins as close to its body as possible, and in some cases, it will be resting on any object in the water including lying on the substrate. In severe cases, the fish may sway with the water current on the surface or on the substrate, and appear almost lifeless as it starts to lay on the side of its body against the substrate.
Clamped fins are a symptom of many different types of bacterial infections and other diseases that can appear in any fish species, regardless of age. Due to this, there isn't much known right from the looks of how the fish reacts besides keeping all of its fins as close to its body as possible (clamped against its body). This is noted to be in order for the fish to not expand the energy to move its fins, in order to reduce the amount of incoming water that flows into their gills, and to prevent the spread of any infection that the fish may have internally (if related to an infection such as a parasite). In a vast majority of cases, it has been noted to be related to poor water quality which would explain why the fish wants as little water movement into its gills, in order to slow down any possible issues with its body from the poor water.
Treatment and Medication
Since this is not a specific disease or infection but a symptom of many, making sure that the water quality is perfect should be the main concern. In many cases having either bad water quality or if the water is either too hot or too cold, many fish will start this behavior to alert their owners that something is wrong. The first step would be to check the water parameters, making sure that the fish is in the correct pH levels, the water temperature is within the correct levels for the species, and if it is a new fish - that it was acclimated correctly (if it shows these signs when added to a different tank, it could be that it is highly stressed and having a hard time getting used to the new water parameters). If the fish is highly sensitive, it is recommended to check parameters across the board that the species may require (such as kH, softness/hardness of the water, flow levels throughout the aquarium to prevent any stagnate areas, etc.).