Religious teacher beginning to train animal (6)
I believe the answer is:
rabbit
'animal' is the definition.
(I've seen this before)
'religious teacher beginning to train' is the wordplay.
'religious teacher' becomes 'rabbi' (Jewish teacher).
'beginning to' says to take the initial letters.
The first letter of 'train' is 't'.
'rabbi'+'t'='RABBIT'
(Other definitions for rabbit that I've seen before include "Bunny; chatter idly" , "Fast-breeding hopper" , "See 17" , "Poor player" , "Meat" .)