When he sings, you'll get the drift (5)
I believe the answer is:
tenor
'drift' is the definition.
(I've seen this before)
'when he sings you'll get the' is the wordplay.
I cannot really see how this works, but
'when' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
The remaining letters 'nor' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tenor that I've seen before include "General meaning of an utterance" , "Voice of Tamino" , "intent" , "Male 17" , "Singer (one of three?)" .)