Nervous and easily upset (6,6)
I believe the answer is:
highly strung
'nervous and easily upset' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for highly strung that I've seen before include "like the violino piccolo" , "Nervous, easily upset" , "Tense and easily upset" , "Excitable - easily upset" , "Very nervous or volatile" .)