In what way can I hide date in google serp for one specific page in my wordpress. I can't figure how to delete it because none date is visible in whole page.
Usually date is got my three places in a web page by the search engines and both are invisible and only one is visible to normal user.
Just view-able text label with date: It will easy to remove since you need to delete the text.
Stored in Meta section of your page/post: You need go to the theme source files and go to appropriate page which can post or single-page & find the meta section for the post and can remove meta tag for date from there.
Stored in Schema if your website use it. You need edit the schema so it does not have a published date.
headsection, in the meta tags. I would check the source code.