One bird of a pair (5)
I believe the answer is:
stilt
'one bird' is the definition.
(stilt is a kind of bird)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for stilt that I've seen before include "bird found on shore" , "Flier" , "Aid for walking tall" , "laboured and unnatural in the past" , "Long-legged wader" .)