Upset, as one is after haircut? (10)
I believe the answer is:
distressed
'one is after haircut?' is the definition.
I can't judge whether this definition defines the answer.
'upset as' is the wordplay.
'upset' becomes 'distress' (distressing is a kind of upseting).
'as' becomes 'ed' (I can't explain this - if you can you should give a lot more credence to this answer).
'distress'+'ed'='DISTRESSED'
(Other definitions for distressed that I've seen before include "Upset; deliberately aged" , "In deep pain or sorrow" , "like Samson when deprived of his strength?" , "in anguish?" , "Anxious" .)