Jump suddenly, brilliant performer put about (5,2)
I believe the answer is:
start up
'jump' is the definition.
(I know that jump is a more specific form of the action start up)
'suddenly brilliant performer put about' is the wordplay.
I cannot really see how this works, but
'brilliant' could be 'star' (star can mean brilliant eg star performer) and 'star' is found within the answer.
an anagram of 'put' is 'tup' which is located in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for start up that I've seen before include "Newly-established business" , "fresh concern" , "Newly-formed company" , "Found" , "get going" .)