Excitable (7)
'excitable' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for nervous that I've seen before include "On edge, anxious" , "Stirred" , "'Apprehensive, uneasy (7)'" , "Twitchy" , "Jumpy" .)
'excitable' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for nervy that I've seen before include "Easily agitated, tense" , "On edge, tense" , "Highly strung" , "Excitable" , "Strained" .)