Headless chaps, almost totally sloshed -- a feature of American sport (3,3)

'a feature of american sport' is the definition.
(type of play in gridiron football)

'headless chaps almost totally sloshed' is the wordplay.
'headless' means to remove the first letter.
'chaps' becomes 'men' (chap means a man).
'almost totally' means to remove the last letter (most but not all of the word).
'sloshed' becomes 'drunk' (sloshed can informally mean drunk).
'men' with its initial letter taken off is 'en'.
'drunk' with its last letter taken off is 'drun'.
'en'+'drun'='END RUN'