To live without you close for so long! (3-3)
I believe the answer is:
bye-bye
'so long' is the definition.
('bye-bye' can be a synonym of 'so long')
'to live without you close' is the wordplay.
'to live' becomes 'be' ('be' can be a synonym of 'live').
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'you' becomes 'ye'.
'close' becomes 'by' (I've seen this in other clues).
'ye'+'by'='yeby'
'be' placed around 'yeby' is 'BYE-BYE'.
'for' acts as a link.
(Other definitions for bye-bye that I've seen before include "Informal repetitive farewell" , "Cheerio" , "Childish farewell" , "Adieu" , "Ciao!" .)