Love and thanks received by fantastic sporting champion (11)
I believe the answer is:
protagonist
'champion' is the definition.
(I know that champion can be written as protagonist)
'love and thanks received by fantastic sporting' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'and' is a charade indicator (letters next to each other).
'thanks' becomes 'ta' (UK informal version of 'thank you').
'received by' is an insertion indicator.
'fantastic' indicates anagramming the letters.
'o'+'ta'='ota'
'sporting' anagrammed gives 'prgonist'.
'ota' put into 'prgonist' is 'PROTAGONIST'.
(Other definitions for protagonist that I've seen before include "Advocate" , "Leading player" , "Leading character in a play, novel, etc" , "champion" , "Hero" .)