One of the family appears at midnight, looking haggard (5)
I believe the answer is:
gaunt
'haggard' is the definition.
('gaunt' can be a synonym of 'haggard')
'one of the family appears at midnight looking' is the wordplay.
I cannot really understand how this works, but
'one' could be 'un' (I've seen this in other clues) and 'un' is found within the answer.
'at' is present in the answer.
'midnight' could be 'g' and 'g' is located in the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for gaunt that I've seen before include "forlorn" , "Lean and haggard" , "Thin and pinched" , "Very thin, cadaverous" , "Drawn" .)