Horrible day? That is about right (4)
I believe the answer is:
dire
'horrible' is the definition.
(thesaurus)
'day? that is about right' is the wordplay.
'day?' becomes 'd' (abbreviation for day).
'that is' becomes 'ie' (synonyms).
'about' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'ie' enclosing 'r' is 'ire'.
'd'+'ire'='DIRE'
(Other definitions for dire that I've seen before include "Ominous; very bad" , "Desperate, horrendous" , "Catastrophic" , "Very serious indeed" , "Of very poor quality" .)