Plain short stage show’s got excess of parts (14)

'excess of parts' is the definition.
(producing too many parts)

'plain short stage show's' is the wordplay.
'plain' becomes 'overt' (both can mean visible or obvious).
'short' means to remove the last letter.
'stage show' becomes 'production' (theatrical production).
'overt' with its last letter taken off is 'over'.
'over'+'production'='OVERPRODUCTION'

'got' acts as a link.