English sides swallowing one team's panacea (6)
I believe the answer is:
elixir
'panacea' is the definition.
(I've seen this in another clue)
'english sides swallowing one team's' is the wordplay.
'english' becomes 'E' (abbreviation as in OED).
'sides' becomes 'LR' (abbreviations for left and right).
'swallowing' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'team' becomes 'XI' (a football team, from Roman numerals for 11).
'i'+'xi'='ixi'
'lr' going around 'ixi' is 'lixir'.
'e'+'lixir'='ELIXIR'
(Other definitions for elixir that I've seen before include "it may be invigorating" , "Magic potion" , "Panacea, nostrum" , "Life-prolonging liquor; panacea" , "This of life was sought by the old alchemist" .)