Football label ruined by the measles (7)
I believe the answer is:
rubella
'the measles' is the definition.
(rubella is a kind of measles)
'football label ruined by' is the wordplay.
'football' becomes 'ru' (I've seen this in other clues).
'ruined' is an anagram indicator.
'by' means one lot of letters go next to another.
'label' with letters rearranged gives 'bella'.
'ru'+'bella'='RUBELLA'
(Other definitions for rubella that I've seen before include "complaint" , "infection" , "German measles" , "contagious disease" .)