Alumnus, upset, is initially on the blower (6)
I believe the answer is:
oboist
'blower' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'alumnus upset is initially on the' is the wordplay.
'alumnus' becomes 'ob' (old boy**).
'upset' indicates an anagram.
'initially' indicates taking the first letters.
The first letters of 'on the' is 'ot'.
'is'+'ot'='isot'
'isot' is an anagram of 'oist'.
'ob'+'oist'='OBOIST'
Can you help me to learn more?
(Other definitions for oboist that I've seen before include "Do I boost the musician?" , "Instrumentalist" , "Wind player" , "Player of woodwind instrument of treble pitch" , "Musician who plays woodwind of treble pitch" .)