Too much activity upset sleuth (6)
I believe the answer is:
hustle
'too much activity' is the definition.
'hustle' can be an answer for 'activity' (hustle is a kind of activity). I'm unsure of the 'too much' bit.
'upset sleuth' is the wordplay.
'upset' indicates anagramming the letters.
'sleuth' anagrammed gives 'HUSTLE'.
Can you help me to learn more?
(Other definitions for hustle that I've seen before include "Push around - deal dishonestly" , "Jostle; hurry; swindle" , "Move along roughly: pester" , "Put pressure on - sleuth (anag)" , "Move furtively - earn forcefully" .)