Apparently these never forget the planes up in the air (9)
I believe the answer is:
elephants
'apparently these never forget' is the definition.
The definition suggests an adverb but the answer is not.
'the planes up in the air' is the wordplay.
'up in the air' indicates an anagram.
'the'+'planes'='theplanes'
'theplanes' is an anagram of 'ELEPHANTS'.
Can you help me to learn more?
(Other definitions for elephants that I've seen before include "Five-toed pachyderms" , "big game" , "See 16" , "The planes (anag.)" , "Largest animals" .)