Flier uncovered book of navigational routes (7)
I believe the answer is:
ortolan
'flier' is the definition.
(ortolan is a kind of birdanimal)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for ortolan that I've seen before include "One flying" , "Flier" , "Bird" , "high-flying singer" , "European bunting" .)