Leading batsman’s first act (6)
I believe the answer is:
opener
I believe this clue is a double definition.
'leading batsman's' is the first definition.
(I've seen this before)
'first act' is the second definition.
(I've seen this in another clue)
(Other definitions for opener that I've seen before include "First batsman in game" , "Leading cricketer" , "Batsman number one" , "Batsman; kitchen utensil" , "Introductory remark" .)