Orca trained to be student of song (5)
I believe the answer is:
carol
'song' is the definition.
(carol is a kind of song)
'orca trained to be student' is the wordplay.
'trained' indicates anagramming the letters (to train can mean to grow something into a shape).
'to be student' becomes 'l' (as in L-plates for learner drivers**).
'orca' anagrammed gives 'caro'.
'caro'+'l'='CAROL'
'of' acts as a link.
(Other definitions for carol that I've seen before include "and 27: Waits" , "Joyful song - woman's name" , "Song, especially at Christmas" , "Joyful hymn" , "sing happily" .)