Empty talk of winning a series? (3)
I believe the answer is:
gas
'empty talk' is the definition.
(I've seen this before)
'of winning a series?' is the wordplay.
'of' says the answer is hidden in the clue.
'GAS' is hidden in the letters of 'winning a series'.
(Other definitions for gas that I've seen before include "person who's amusing ..." , "Form of fossil fuel" , "eg CO2" , "may fill American car" , "Neon, for example" .)