The plane flying is a Jumbo (8)
I believe the answer is:
elephant
'a jumbo' is the definition.
(thesaurus)
'the plane flying' is the wordplay.
'flying' indicates an anagram.
'the'+'plane'='theplane'
'theplane' anagrammed gives 'ELEPHANT'.
'is' acts as a link.
(Other definitions for elephant that I've seen before include "bigger one from two continents?" , "See 18" , "Tusked mammal" , "The symbol of the Republican Party" , "Trunk on one" .)