Eagerly excited by a good turn around (4)
I believe the answer is:
agog
'eagerly excited' is the definition.
(I've seen this before)
'a good turn around' is the wordplay.
'a good' becomes 'ag' (I've seen this in other clues).
'turn' becomes 'go' (a person's move in a board game).
'around' is a reversal indicator.
'go' backwards is 'og'.
'ag'+'og'='AGOG'
'by' is the link.
(Other definitions for agog that I've seen before include "Eager and wide-eyed" , "Wide-eyed and amazed" , "Impatient" , "Very curious to hear" , "Very eager (to see or hear something)" .)