Brave nobleman in iron shackles, gutted (8)
I believe the answer is:
fearless
'brave' is the definition.
(synonyms)
'nobleman in iron shackles gutted' is the wordplay.
'nobleman' becomes 'earl' (earl is a kind of nobleman).
'in' means one lot of letters goes inside another.
'iron' becomes 'fe' (Fe is the chemical symbol for iron).
'gutted' says to hollow out the word (remove centre letters) (to gut something is to remove its insides).
'shackles' with its middle taken out is 'ss'.
'earl' placed inside 'fe' is 'fearle'.
'fearle'+'ss'='FEARLESS'
(Other definitions for fearless that I've seen before include "Totally courageous" , "Stout-hearted" , "Intrepid" , "Indomitable" , "Hardy" .)