Unresolved detail (5,3)
I believe the answer is:
loose end
'unresolved detail' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for loose end that I've seen before include "'A detail not settled or explained (5,3)'" , "unfinished work" , "should have been tied?" , "As yet unexplained detail" , "Detail not yet settled" .)