Fervent participator in craze -- a lottery (6)
I believe the answer is:
zealot
'fervent participator' is the definition.
(a zealous or passionate person)
'in craze a lottery' is the wordplay.
'in' says the answer is hidden in the clue.
'ZEALOT' can be found hidden inside 'craze a lottery'.
(Other definitions for zealot that I've seen before include "A fanatic or extremist" , "Fanatic, fiery follower" , "Over-zealous person, fanatic" , "A fanatic or over-enthusiastic person" , "One ardent for cause" .)