Terrible flaw, maybe around mid-January (5)
I believe the answer is:
awful
'terrible' is the definition.
('awful' can be a synonym of 'terrible')
'flaw maybe around mid-january' is the wordplay.
'maybe' is an anagram indicator.
'around' means one lot of letters goes inside another.
'mid' says to take the centre.
The middle of 'january' is 'u'.
'flaw' anagrammed gives 'awfl'.
'awfl' placed around 'u' is 'AWFUL'.
(Other definitions for awful that I've seen before include "Extremely bad or unpleasant" , "Not good at all" , "Fearsome" , "Atrocious, dire" , "Horrific" .)