The planes compromised those with trunks? (9)
I believe the answer is:
elephants
'those with trunks?' is the definition.
I can't judge whether this defines the answer.
'the planes compromised' is the wordplay.
'compromised' indicates an anagram (I've seen 'compromising' mean this (compromise can mean change)).
'the'+'planes'='theplanes'
'theplanes' with letters rearranged gives 'ELEPHANTS'.
Can you help me to learn more?
(Other definitions for elephants that I've seen before include "Jumbos" , "Animals from the palest hen" , "big game" , "Largest animals" , "The planes (anag.)" .)