If we take a clitic as a part of word that is attached after the ending and attached to the word depending on the word order (examples include -'s in English and -que in Latin), what would be definite articles in languages such as Bulgarian and Danish? Are they clitics or endings?
Of course, the distinction between clitics and affixes is not accepted by all linguists.
But for people who do find it meaningful, I have the impression that postposed definite articles are often called clitics, but have been argued to actually be suffixes instead. See "Romanian definite articles are not clitics", by Albert Ortmann & Alexandra Popescu, and the question Why is the definite article in Balkan languages always called a suffix when it really seems to be part of the inflection?
The status of articles in North Germanic languages seem to be similarly dubious or arguable.