Rearing bats in wild to a greater extent (7)
I believe the answer is:
angrier
'wild to a greater extent' is the definition.
('wild' can mean 'angry')
'rearing bats' is the wordplay.
'bats' indicates an anagram (slang for mad).
'rearing' with letters rearranged gives 'ANGRIER'.
'in' is the link.
(Other definitions for angrier that I've seen before include "More furious" , "more outraged" , "More annoyed" , "More irate" , "Not so calm" .)