Let tyro run raffle (7)
I believe the answer is:
lottery
'raffle' is the definition.
(I've seen this before)
'let tyro run' is the wordplay.
'run' indicates an anagram.
'let'+'tyro'='lettyro'
'lettyro' anagrammed gives 'LOTTERY'.
(Other definitions for lottery that I've seen before include "Random selection" , "Random prize game" , "A means of raising funds" , "Chance draw" , "Sweepstake" .)