To be starting trouble is a chancy thing (3)
I believe the answer is:
bet
'a chancy thing' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'to be starting trouble' is the wordplay.
'starting' suggests taking the first letters.
The initial letter of 'trouble' is 't'.
'be'+'t'='BET'
'is' is the link.
Can you help me to learn more?
(Other definitions for bet that I've seen before include "Money risked on a gamble" , "Wager, back" , "Wager, or the sum waged" , "Speculation" , "'Stake, wager (3)'" .)