Primate voiced displeasure entering bar (6)
I believe the answer is:
baboon
'primate' is the definition.
(I know that baboon is a type of Old World monkey)
'voiced displeasure entering bar' is the wordplay.
'voiced displeasure' becomes 'boo' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'entering' means one lot of letters goes inside another.
'bar' becomes 'ban' (both can mean to outlaw or block).
'boo' put within 'ban' is 'BABOON'.
Can you help me to learn more?
(Other definitions for baboon that I've seen before include "Large long-nosed African or Asian monkey" , "animal" , "Large primate" , "A large one of 17 across" , "wild swinger?" .)