A supporter who arouses enthusiasm (11)
I believe the answer is:
cheerleader
'a supporter' is the definition.
(I know that cheerleader is a type of supporter)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for cheerleader that I've seen before include "Enthusiastic type" , "Orchestrator of applause" , "Support director" , "Organiser of support for a sports team" , "figure offering vocal support?" .)