Competitor very invested in Middle East cash (5)
I believe the answer is:
rival
'competitor' is the definition.
(I know that contestant is a type of competitor)
'very invested in middle east cash' is the wordplay.
'very' becomes 'v' (common abbreviation).
'invested in' indicates putting letters inside.
'middle east cash' becomes 'rial' (I am not sure about this - if you are sure you should believe this answer much more).
'v' inserted into 'rial' is 'RIVAL'.
Can you help me to learn more?
(Other definitions for rival that I've seen before include "Adversary, antagonist" , "Competitor; be as good as" , "Emulate" , "Adversary or foe" , "Contestant you hope to defeat" .)