Cycling parasite, a high-flyer (5)
I believe the answer is:
ousel
'flyer' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for ousel that I've seen before include "dipper" , "Bird similar to blackbird" , "Bird; louse (anag.)" , "Singer" , "Former name for blackbird" .)