Pole -- maybe bats are up one (8)
I believe the answer is:
european
'pole maybe' is the definition.
(I know that Pole is a type of European)
'bats are up one' is the wordplay.
'bats' indicates an anagram (slang for mad).
'are'+'up'+'one'='areupone'
'areupone' is an anagram of 'EUROPEAN'.
(Other definitions for european that I've seen before include "Relating to the continent" , "Native of a continent" , "Inhabitant of the second smallest continent" , "Dubliner, Londoner, Berliner, for instance" , "Continental inhabitant" .)