Baseball player's pants and shirt? (9)
I believe the answer is:
shortstop
'baseball player's' is the definition.
(shortstop is a kind of baseball player)
'pants and shirt?' is the wordplay.
'pants' becomes 'shorts' (shorts is a kind of pants).
'and' is a charade indicator (letters next to each other).
'shirt?' becomes 'top'.
'shorts'+'top'='SHORTSTOP'
(Other definitions for shortstop that I've seen before include "Opening move" , "Fielding position (baseball)" , "Fielder in baseball" , "US player" , "One in field" .)