Permitted to leave starter that's horrible (5)
I believe the answer is:
awful
'horrible' is the definition.
(I've seen this before)
'permitted to leave starter' is the wordplay.
'permitted' becomes 'lawful' (I've seen this before).
'to leave' suggests deleting specific letters.
'starter' becomes 'l'.
'lawful' with 'l' taken out is 'AWFUL'.
'that's' is the link.
(Other definitions for awful that I've seen before include "Dreadful and dire" , "Very embarrassing" , "Dreadful - spine-chilling" , "Very poor" , "Dreadful, really bad" .)