Characters in flamboyant unicyclist's garment (5)
I believe the answer is:
tunic
'garment' is the definition.
(tunic is a kind of garment)
'characters in flamboyant unicyclist's' is the wordplay.
'characters in' indicates the answer is hidden within the clue.
'TUNIC' can be found hidden inside 'flamboyant unicyclist'.
(Other definitions for tunic that I've seen before include "Jacket of some soldiers" , "(Policeman's) jacket" , "Shift" , "School garment" , "Schoolgirl's dress" .)