The word that means the same as "nark" is irritate.

Explanation:

• Nark: This word is a slang term that means to annoy or irritate someone. It often implies a minor, ongoing annoyance.
• Obligation: This means a duty or responsibility that one is bound to fulfill.
• Reassure: This means to restore confidence or dispel doubts.
• Solace: This means comfort or consolation in a time of distress or sadness.

Therefore, based on the definitions, "irritate" is the closest in meaning to "nark."