Awful singer finally accepted by choir, if desperate (8)
I believe the answer is:
horrific
'awful' is the definition.
(I know that awful can be written as horrific)
'singer finally accepted by choir if desperate' is the wordplay.
'finally' suggests the final letters.
'accepted by' is an insertion indicator.
'desperate' indicates an anagram (a desperate or pathetic spelling).
The last letter of 'singer' is 'r'.
'choir'+'if'='choirif'
'choirif' is an anagram of 'horific'.
'r' going inside 'horific' is 'HORRIFIC'.
(Other definitions for horrific that I've seen before include "Dreadful, horrendous" , "Inspiring intense fear" , "Appalling" , "Dire" , "Arousing feelings of shock and fear" .)