In The Next Generation episode "Sins of the Father", Duras says to Worf,
"Yet you come here in a child's uniform and you bring outsiders to our great halls."
What was Worf wearing that Duras called a child's uniform?
Something he wore as a child at Khitomer? According to Memory Alpha, Worf was 6 years old at the time of the Khitomer massacre. How would an adult Worf be able to wear such a child-sized item?
His baldric? Worf wears it throughout two series, and it is an adult size. (It does, however, change color between TNG seasons 1 and 2.)
His Starfleet uniform? In that case, wouldn't Klingons disparage all Starfleet uniforms as a child's uniform?
The sleeveless Klingon cloak he wears over his Starfleet uniform? Unlikely, as other members of the High Council and Duras also wear the same garment (see picture below).
Question regarding a later episode: When did Worf get a Klingon uniform?