It's actions. "Practice what you preach" is a standard phrase in English. It means your actions should match what you say, especially related to doing right right thing. Example: If man publicly advocates for women's rights, but he treats his wife and daughters terribly, you could say, "You need to practice what you preach."

It means, 'do' the same things that you tell other people to do. Instead of doing one thing and telling other people to do the opposite. People who make this mistake sometimes apologise for it by saying 'do what I say, not what I do'. People who witness this mistake sometimes call it out by saying 'practise what you preach'. Note, practise (verb) has an 's' in British English, while the noun (a practice, for example, a medical practice, meaning a medical centre) has no 's'. Meanwhile in American English both versions have no 's'.

It's a verb in this sentence.