Fuel spoken of for flier (6)
I believe the answer is:
petrel
'flier' is the definition.
(petrel is a kind of birdanimal)
'fuel spoken of' is the wordplay.
'fuel' becomes 'petrol' (petrol is a kind of fuel).
'spoken of' indicates a 'sounds like' (homophone) clue.
'petrol' sounds like 'PETREL'.
'for' is the link.
(Other definitions for petrel that I've seen before include "Small seabird" , "18's [BIRD]" , "Mother Carey's chicken" , "Storm bird" , "Seabird (that may be stormy)" .)