In the wild, they don't contrive to save gas (7)
I believe the answer is:
savages
'in the wild' is the definition.
I can't tell whether this definition defines the answer.
'they don't contrive to save gas' is the wordplay.
'save gas' can be anagrammed to 'SAVAGES'.
However, I am not clear how this is indicated.
Can you help me to learn more?
(Other definitions for savages that I've seen before include "More than one brutal person" , "Barbarians" .)