Say, a call in court is rejected by union instruction (8)
'instruction' is the definition.
(tutelage is instructing or teaching)
'say a call in court is rejected by union' is the wordplay.
I cannot really see how this works, but
'a' is within the answer.
'call' could be 'tel' (short for telephone) and 'tel' is found within the answer.
'union' could be 'tu' (I've seen this in other clues) and 'tu' is found in the answer.
The remaining letters 'ge' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for tutelage that I've seen before include "Schooling", "Training", "guidance", "Instruction by personal teacher", "Tuition".)