Dreadful, terrible (4)
I believe the answer is:
dire
I believe this clue is a double definition.
'dreadful' is the first definition.
(I know that dreadful can be written as dire)
'terrible' is the second definition.
(I know that terrible can be written as dire)
(Other definitions for dire that I've seen before include "Desperate, horrendous" , "Really dreadful - ride on" , "Ride in dreadful state" , "Desperate; dreadful" , "to speak (13) [FRENCH]" .)