Striving to become troublesome (6)
I believe the answer is:
trying
'troublesome' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for trying that I've seen before include "Taxing" , "Stressful" , "What could be witnessed in court" , "Testing" , "Essaying" .)