Back with girlfriend, initially excited (4)
I believe the answer is:
agog
'excited' is the definition.
(similar in meaning)
'back with girlfriend initially' is the wordplay.
'back' becomes 'ago' ('years back' means 'years ago').
'with' means one lot of letters go next to another.
'initially' suggests taking the first letters.
The first letter of 'girlfriend' is 'g'.
'ago'+'g'='AGOG'
(Other definitions for agog that I've seen before include "Perfect" , "Enthralled" , "Wide-eyed in anticipation" , "Eager - in suspense" , "Wide-eyed and amazed" .)