Wrong football team has managed to lose? Rats! (7)
I believe the answer is:
singers
'managed to lose? rats' is the definition.
I can't judge whether this definition defines the answer.
'wrong football team' is the wordplay.
'wrong' becomes 'sin' (I've seen this before).
'football team' becomes 'gers' (I am not sure about this - if you are sure you should believe this answer much more).
'sin'+'gers'='SINGERS'
'has' is the link.
Can you help me to learn more?
(Other definitions for singers that I've seen before include "Chorus" , "Choristers" , "eg Tenors" , "Vocalists" , "See 26" .)