Terrible flaw, maybe around mid-January (5)
I believe the answer is:
awful
'terrible' is the definition.
(synonyms)
'flaw maybe around mid-january' is the wordplay.
'maybe' indicates anagramming the letters.
'around' indicates putting letters inside.
'mid' indicates the central letters (mid- can mean the middle of something).
The middle letter of 'january' is 'u'.
'flaw' with letters rearranged gives 'awfl'.
'awfl' enclosing '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" .)