Definition queries are (still!) not supported with WFS services.
To quote the documentation from http://server.arcgis.com/en/server/latest/publish-services/windows/wfs-services.htm
"The map document is just a specification of the layers that will be available in your WFS service. Symbology, query definitions, and field aliases defined at the layer level do not transfer to the WFS service, because the purpose of the service is to expose the features in the data."
The two solutions I've used for this is either a product over the top of the WFS services (shout out to con Terra), or implementing the definition queries in views in the enterprise GDB.