What region are you in?
Artists and more specifically the song distributor uploads the song and determines what regions they want to make it available along with adding a Clean/Explicit tag. It is possible for them to tag a song as Explicit and still censor content in the song that they upload and regions can also see different versions of songs.
I would suggest making contact with the Artist/Distributor to see if there was a mistake made in the song they uploaded or if it was an intentional action.
You can file a complaint with Apple if a song tagged as Clean contains Explicit language, but there is nothing saying a song marked as Explicit must contain the inappropriate language. Apple does not make a song uploaded as Explicit a Clean song by censoring, it is the Artist/Distributor that must upload that version of the song. That is also why you may see some songs that are only Explicit as they have chosen not to upload a Clean version.