Challenge a Red, perhaps (4)
I believe the answer is:
dare
'challenge' is the definition.
(dare is a kind of challenge)
'a red perhaps' is the wordplay.
'perhaps' is an anagram indicator.
'a'+'red'='ared'
'ared' anagrammed gives 'DARE'.
(Other definitions for dare that I've seen before include "Be brave enough" , "Challenge to do something dangerous" , "Take the risk, face the danger" , "Take a chance - read about it" , "Challenge of courage" .)