Gloomy supporters will, if their team's doing badly (9)
I believe the answer is:
cheerless
'gloomy' is the definition.
(similar in meaning)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for cheerless that I've seen before include "not hip?" , "Miserable" , "Dreary" , "Gloomy, depressing" , "Bleak" .)