Incredibly wayward serve gets over (4,2)
I believe the answer is:
ever so
'incredibly' is the definition.
'wayward serve gets over' is the wordplay.
'wayward' is an anagram indicator.
'gets' is a charade indicator (letters next to each other).
'over' becomes 'o' (cricket abbreviation).
'serve' is an anagram of 'evers'.
'evers'+'o'='EVER SO'
(Other definitions for ever so that I've seen before include "To a very great extent" , "Jolly" , "Intensifier" , "Extremely" , "Very much" .)