I'm in a race - go! (9)
I believe the answer is:
animation
'go' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'i'm in a race' is the wordplay.
'in' means one lot of letters goes inside another.
'race' becomes 'nation' (both can mean a national or ethnic group).
'a'+'nation'='anation'
'im' inserted inside 'anation' is 'ANIMATION'.
Can you help me to learn more?
(Other definitions for animation that I've seen before include "Liveliness and enthusiasm" , "Vigour; film technique" , "Art of cartoon making" , "Film technique; lively state" , "Cartoon-making art" .)