Pitch high one initially, resulting in dismissal (5-2)
I believe the answer is:
heave-ho
'dismissal' is the definition.
(I've seen this before)
'pitch high one initially' is the wordplay.
'pitch' becomes 'heave' (both can mean to throw).
'initially' indicates taking the first letters.
The initial letters of 'high one' is 'ho'.
'heave'+'ho'='HEAVE-HO'
'resulting in' acts as a link.
(Other definitions for heave-ho that I've seen before include "Cry accompanying physical effort" , "Get ready to lift" , "The push" , "elbow" , "Rejection" .)