Trip out entertaining revolutionary baseball player (7)
I believe the answer is:
'baseball player' is the definition.
(pitcher is a kind of baseball player)
'trip out entertaining revolutionary' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'entertaining' is an insertion indicator.
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'trip' with letters rearranged gives 'pitr'.
'pitr' enclosing 'che' is 'PITCHER'.
(Other definitions for pitcher that I've seen before include "source of drink?" , "large vessel" , "one getting walked all over?" , "Earthenware vessel" , "Baseball thrower or water jug" .)