Brave man - one embraced by big bird (6)
I believe the answer is:
heroic
'brave' is the definition.
(thesaurus)
'man one embraced by big bird' is the wordplay.
'man' becomes 'he'.
'one' becomes 'i' (Roman numeral).
'embraced by' indicates putting letters inside.
'big bird' becomes 'roc' (I've seen this before).
'i' going within 'roc' is 'roic'.
'he'+'roic'='HEROIC'
(Other definitions for heroic that I've seen before include "Supremely courageous and brave" , "Of deed or person, very brave" , "lion-hearted" , "Dramatic" , "Very brave and noble" .)