Free lass, terribly brave (8)
I believe the answer is:
fearless
'brave' is the definition.
('fearless' can be a synonym of 'brave')
'free lass terribly' is the wordplay.
'terribly' indicates anagramming the letters.
'free'+'lass'='freelass'
'freelass' is an anagram of 'FEARLESS'.
(Other definitions for fearless that I've seen before include "Confident" , "Intrepid" , "Ignoring danger and peril" , "game?" , "Stout-hearted" .)