Henry V performance finally split into two parts (5)
I believe the answer is:
halve
'split into two parts' is the definition.
'henry v performance finally' is the wordplay.
'henry' becomes 'hal'.
'finally' says to take the final letters.
The final letter of 'performance' is 'e'.
'hal'+'v'+'e'='HALVE'
(Other definitions for halve that I've seen before include "Split in two" , "cut by fifty percent" , "Divide into two equal parts" , "Divide into two equal pieces" , "make 10 5 say?" .)