Strange, unknown primate at peak (4)
I believe the answer is:
apex
'peak' is the definition.
(I know that peak can be written as apex)
'strange unknown primate' is the wordplay.
I cannot really understand how this works, but
'unknown' could be 'x' (algebra) and 'x' is located in the answer.
'primate' could be 'ape' (large primate) and 'ape' is present in the answer.
No letters remain.
This explanation may well be incorrect...
'at' is the link.
Can you help me to learn more?
(Other definitions for apex that I've seen before include "Uppermost tip" , "Point or summit" , "climax" , "The highest point of something" , "reasonable fare" .)