Challenging someone to be bold (6)
I believe the answer is:
daring
This could be a double definition.
'challenging someone' is the first definition.
'daring' can be an answer for 'challenging' (daring is a kind of challenging). I'm not sure about the 'someone' bit.
'bold' is the second definition.
(I've seen this before)
'to be' is the link.
Can you help me to learn more?
(Other definitions for daring that I've seen before include "Courageous" , "Challenging or defying" , "Intrepid" , "'Adventurous, bold (6)'" , "Boldly dramatic or unconventional" .)