Small band (7)
(Other definitions for circlet that I've seen before include "Small round shape" , "Metal band" , "Little hoop" , "Diadem" , "Ornamental headband" .)
'small band' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for trio that I've seen before include "wise men?" , "Group of Magi?" , "Ensemble musical piece, eg Beethoven's 'Archduke'" , "Threesome" , "Three of a kind" .)