Administer contest on the radio (4)
I believe the answer is:
mete
'administer' is the definition.
(thesaurus)
'contest on the radio' is the wordplay.
'contest' becomes 'meet' (meet is a kind of contest).
'on the radio' indicates a 'sounds like' (homophone) clue.
'meet' sounds like 'METE'.
(Other definitions for mete that I've seen before include "Administer or hand out" , "Administer or bestow, as in small portions" , "Dish (out)" , "Dole (out)" , "boundary" .)