A bird used merely as decoration (5)
I believe the answer is:
braid
'decoration' is the definition.
(braid is a kind of decoration)
'a bird used' is the wordplay.
'used' is an anagram indicator.
'a'+'bird'='abird'
'abird' with letters rearranged gives 'BRAID'.
'merely as' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for braid that I've seen before include "Woven ornamental trimming or plait of hair" , "Woven ornamental trimming, often gold" , "Ornamental strip" , "Decorative ribbon" , "Ornamental tape or plait" .)