A hang-up that's worrying son — close to collapse following mother's remark (5,2,8)
I believe the answer is:
sword of damocles
'a hang-up that's worrying' is the definition.
(sword of Damocles means something hanging over you)
'son close to collapse following mother's remark' is the wordplay.
I cannot really see how this works, but
'son' could be 's' (genealogical abbreviation for son) and 's' is found in the answer.
an anagram of 'close' is 'ocles' which is present in the answer.
'following' could be 'f' (used when citing page numbers etc) and 'f' is found within the answer.
'mother' could be 'dam' (female parent of an animal) and 'dam' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for sword of damocles that I've seen before include "precarious situation" , "Impending threat" , "Imminently impending peril, disaster" , "It was perilously poised overhead" , "imminent threat" .)