Bold, or at first lost in terrible perdition (8)
I believe the answer is:
intrepid
'bold' is the definition.
(similar in meaning)
'at first lost in terrible perdition' is the wordplay.
'at' becomes 'in'.
'first lost in terrible perdition' becomes 'trepid' (I can't explain this - if you can you should believe this answer much more).
'in'+'trepid'='INTREPID'
'or' acts as a link.
Can you help me to learn more?
(Other definitions for intrepid that I've seen before include "I printed this way, being daring" , "'Brave, dauntless (8)'" , "Afraid not" , "Unfearing" , "Bold" .)