A motor sport picking up after a period of decline (8)
I believe the answer is:
rallying
'a motor sport' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for rallying that I've seen before include "Cry after this" , "making recovery" , "Gathering" , "staging recovery" , "Motorsport" .)