hornet's nest
US /ˈhɔːr.nɪts ˌnest/
UK /ˈhɔːr.nɪts ˌnest/

1.
a nest of hornets
:
•
Be careful not to disturb the hornet's nest in the attic.
•
The children found a large hornet's nest hanging from the tree branch.
2.
a difficult or unpleasant situation that is likely to cause a lot of trouble or anger if it is disturbed
:
•
Bringing up that topic in the meeting was like stirring up a hornet's nest.
•
The new policy proposal has stirred up a real hornet's nest among the employees.