First night - very jittery (5)
I believe the answer is:
'first night very jittery' is the definition.
I can't tell whether this defines the answer.
'first night very jittery' is the wordplay.
'first night' becomes 'n' (1st letter of 'night').
'jittery' is an anagram indicator.
'very' is an anagram of 'ervy'.
Can you help me to learn more?
(Other definitions for nervy that I've seen before include "Highly-strung" , "On edge, tense" , "Easily agitated, tense" , "Anxious, jumpy" , "Highly strung" .)