At the crux of it, nobody counts concerns about jump (6)
I believe the answer is:
bounce
'jump' is the definition.
(I know that bounce is a type of jump)
'at the crux of it nobody counts concerns about' is the wordplay.
I cannot quite understand how this works, but
'of' could be 'o' and 'o' is present in the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is present in the answer.
'about' could be 'c' (circa) and 'c' is found in the answer.
The remaining letters 'bun' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bounce that I've seen before include "What a cheque may do if there are insufficient funds" , "Showing self-confidence" , "Spring back like a rubber ball" , "Springiness" , "Reflect back from a surface" .)