Nervous, say, around beginning of day and end of day (4)
I believe the answer is:
edgy
'nervous' is the definition.
('edgy' can be a synonym of 'nervous')
'say around beginning of day and end of day' is the wordplay.
'say' becomes 'eg' (**).
'around' means one lot of letters goes inside another.
'beginning of' indicates taking the first letters.
'and' says to put letters next to each other.
'end of' says to take the final letters.
The initial letter of 'day' is 'd'.
The final letter of 'day' is 'y'.
'eg' going around 'd' is 'edg'.
'edg'+'y'='EDGY'
(Other definitions for edgy that I've seen before include "Challengingly experimental" , "Apprehensive" , "Sharp in outline" , "Red shade" , "Nervous and tense, irritable" .)