Figure possibly to make a liar out of a competitor (5)
I believe the answer is:
rival
'a competitor' is the definition.
(I know that challenger can be written as rival)
'figure possibly to make a liar out' is the wordplay.
'figure possibly' becomes 'v' (I can't justify this - if you can you should believe this answer much more).
'to make' indicates anagramming the letters.
'out' indicates putting letters inside.
'liar' anagrammed gives 'rial'.
'v' going into 'rial' is 'RIVAL'.
'of' is the link.
Can you help me to learn more?
(Other definitions for rival that I've seen before include "Someone you hope to defeat" , "Close competitor" , "Contender" , "Adversary, antagonist" , "Be equal to in quality" .)