new disciple; new student; new apprentice
General term for a newly accepted follower or trainee in traditional arts, crafts, or disciplines.
newly accepted professional wrestler (sumo)
Specifically used in sumo for a newly recruited wrestler who has just joined a stable.
He entered as a new disciple of flower arrangement this year.
The new wrestler stepped onto the ring for the first time.
新入生 is used for new students in schools, whereas 新弟子 is for traditional apprenticeship or sumo contexts.
sumo recruit physical exam
Compound of 新 (new) and 弟子 (disciple, apprentice). The reading しんでし follows standard on'yomi for 新 and kun'yomi for 弟子.