Is there a way to apply a filter after importing a feature from a file to ArcGIS Online?

Yes. To make the Filter option visible, publish the feature as a hosted feature layer or feature service. Filters can only be created on hosted feature layers, ArcGIS Server feature service layers, and ArcGIS Server map service layers that have associated attribute data.

Files such as CSV files, shapefiles, or GPS Exchange Format (GPX) files are not hosted feature layers when imported to ArcGIS Online. However, any feature collection imported from a file can be published from the Item Details page as a hosted feature service.

For more information on publishing a map feature as a hosted service layer, refer to the following ArcGIS Online Web Help topic, Publish features.

Note:
Publishing a map requires users to have privileges to create content and publish hosted feature layers. For more information on role privileges, refer to the following ArcGIS Web Help topic, Organization roles.