Top men aim to be cast in Christmas entertainment (9)
I believe the answer is:
pantomime
'christmas entertainment' is the definition.
(I've seen this before)
'top men aim to be cast' is the wordplay.
'to be cast' is an anagram indicator (letters are dispersed or cast around).
'top'+'men'+'aim'='topmenaim'
'topmenaim' anagrammed gives 'PANTOMIME'.
'in' is the link.
(Other definitions for pantomime that I've seen before include "Mime on tap in children's show" , "Farcical situation" , "eg 'Mother Goose'" , "farce" , "Festive stage show" .)