Performer's nervousness (5,6)
I believe the answer is:
stage fright
'performer's nervousness' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stage fright that I've seen before include "Actor's fear" , "Pre-performance nerves" , "attack of nerves" , "Performer's nervousness" , "state of nerves" .)