loose end

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A minor unresolved problem or difficulty, especially a final detail preceding the completion of something.
• idiom (at loose ends) Without a clear purpose or regular occupation; unsettled in one's affairs.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The end of a rope that has not been fastened.
• noun idiomatic, by extension A small job that needs to be done, or minor problem that needs to be resolved, before a task can be considered complete.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun work that is left incomplete