Pain of one of those giants from Bunyan's The Pilgrim's Progress (7)
I believe the answer is:
despair
'pain' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for despair that I've seen before include "Complete absence of hope" , "First appearance" , "Opposite of 10" , "Total loss of hope" , "Abandon hope" .)