Rush over, showing enthusiasm (5)
I believe the answer is:
gusto
'enthusiasm' is the definition.
(I know that gusto is a type of enthusiasm)
'rush over' is the wordplay.
'rush' becomes 'gust' (I have seen 'Rush of wind ' mean 'gust' so perhaps 'rush' could also mean 'gust').
'over' becomes 'o' (cricket abbreviation).
'gust'+'o'='GUSTO'
'showing' acts as a link.
(Other definitions for gusto that I've seen before include "Relish; vigour" , "Obvious enthusiasm" , "Hearty enjoyment" , "Showing zest" , "Vigorous and enthusiastic enjoyment" .)