Fellows scored after upsetting drink (6)
I believe the answer is:
decaff
'drink' is the definition.
'fellows scored after upsetting' is the wordplay.
'fellows' becomes 'ff' (an abbreviation for fellow written twice).
'scored' becomes 'aced' (acing is a kind of scoring).
'after upsetting' shows that the letters should be reversed in order (in a down clue, letters go up).
'ff'+'aced'='ffaced'
'ffaced' reversed gives 'DECAFF'.
(Other definitions for decaff that I've seen before include "Coffee without the kick" , "Type of coffee (colloq.)" .)