Linguistisessä
Linguistisessä is not a distinct field or concept in linguistics, but rather a form of the Finnish adjective lingvistinen, which means “linguistic.” In standard Finnish, the adjective is used to describe things related to linguistics, language, or the study of language. The form linguististinen appears in compounds and phrases, most commonly in the inessive case, for example lingvistisessä tutkimuksessa meaning “in linguistic research.”
In Finnish, adjectives of the -inen type inflect for case and number, so lingvistinen becomes lingvistisen (genitive),
If "Linguistisessä" appears capitalized, it is unlikely to refer to a widely recognized concept in linguistics.
See also: linguistics in Finnish (kielitiede), the noun lingvistiikka, and the adjective lingvistinen.