Almost be bold enough to succeed famous scientist (6)
I believe the answer is:
darwin
'famous scientist' is the definition.
(Charles Darwin)
'almost be bold enough to succeed' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'be bold enough to' becomes 'dare' (I've seen this before).
'succeed' becomes 'win' (succeed can mean to win or excel).
'dare' with its final letter taken off is 'dar'.
'dar'+'win'='DARWIN'
(Other definitions for darwin that I've seen before include "Evolution scientist and city" , "Author of The Descent of Man" , "He propounded the Theory of Evolution" , "Aussie city" , "Charles . . . . . ., great scientist of evolution" .)