Wise ape isn't going berserk (7)
I believe the answer is:
sapient
'wise' is the definition.
(similar in meaning)
'ape isn't going berserk' is the wordplay.
'going berserk' indicates an anagram.
'ape'+'isnt'='apeisnt'
'apeisnt' is an anagram of 'SAPIENT'.
(Other definitions for sapient that I've seen before include "Canny" , "very keen" , "Snipe at, being wise" , "Having intelligence" , "Discerning" .)