harrastuslikusta
Harrastuslikusta is not a standard Finnish word and does not appear in major dictionaries. When it is encountered, it is usually considered a nonstandard inflected form built from harrastus (hobby) with an imagined adjective stem harrastuslik-, plus the elative ending -sta. In that reading, harrastuslikusta would roughly mean “from the hobby-like [something],” and would appear inside a larger phrase such as harrastuslikusta toiminnasta, depending on context. However, such a construction is not idiomatic in contemporary, standard Finnish.
The form likely reflects either a dialectal variant, a typographical error, or a calque from another language
In standard Finnish, more common ways to express related ideas would be to use harrastuksesta to indicate