Silly ape isn't wise (7)
I believe the answer is:
sapient
'wise' is the definition.
(similar in meaning)
'silly ape isn't' is the wordplay.
'silly' indicates an anagram.
'ape'+'isnt'='apeisnt'
'apeisnt' anagrammed gives 'SAPIENT'.
(Other definitions for sapient that I've seen before include "Discerning" , "Canny" , "Snipe at (anag.)" , "Snipe at, being wise" , "Acutely insightful and wise" .)