Start seeing bouncy character filled with despair ultimately (7)
I believe the answer is:
trigger
'start' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for trigger that I've seen before include "Releasing device" , "Gun-firing device" , "arm with this?" , "Set in motion - say gunfire" , "Roy Rogers' horse" .)