Footballers court alternative agent (6)
I believe the answer is:
factor
'agent' is the definition.
(business term for a representative)
'footballers court alternative' is the wordplay.
'footballers' becomes 'fa' (Football Association abbreviation).
'court' becomes 'ct'.
'alternative' becomes 'or'.
'fa'+'ct'+'or'='FACTOR'
(Other definitions for factor that I've seen before include "One circumstance that contributes to a result" , "Thirteen is one of fifty two" , "Circumstance that influences result" , "Act for (anag)" , "Circumstance that contributes towards a result" .)