Nervous individual departs, say, after returning (2,4)
I believe the answer is:
on edge
'nervous' is the definition.
(I've seen this before)
'individual departs say after returning' is the wordplay.
'individual' becomes 'one' (an individual is one person).
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'say' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'after returning' says the letters should be written in reverse.
'eg' written backwards gives 'ge'.
'one'+'d'+'ge'='ON EDGE'
(Other definitions for on edge that I've seen before include "Nervously excited" , "Tense and irritable, very nervous" , "close to border" , "Anxious, nervy" , "Nervous and tense - close to cliff?" .)