Chinese puzzle
ado
aggravation
annoyance
anxiety
bad news
baffle
bafflement
baffling problem
basis
bedevilment
besetment
bewilderment
blemish
bone of contention
bore
bother
botheration
bothersomeness
brain twister
bug
bugaboo
bugbear
burden
can of worms
case
catch
catechism
chapter
complication
concern
confoundment
confusion
conundrum
count
crack
crashing bore
cross-interrogatory
cross-question
crossword puzzle
crux
debating point
defect
defection
deficiency
delinquent
demand
devilment
difficult
difficulty
issue
need
process
question
result
situation
solution