片断 is a noun meaning a fragment, segment, or part of a larger whole — such as a piece of a conversation, a clip from a film, or a section of a document. You can use it with measure words like 一个片断 or 这段片断. Although the word can also function as an adjective meaning 'fragmentary' or 'incomplete' in some contexts, this row is labeled as a noun, so stick to noun usage.