Summit making primate cross (4)
I believe the answer is:
apex
'summit' is the definition.
(thesaurus)
'primate cross' is the wordplay.
'primate' becomes 'ape' (I've seen this before**).
'cross' becomes 'x'.
'ape'+'x'='APEX'
'making' acts as a link.
(Other definitions for apex that I've seen before include "Top point" , "climax" , "The highest point or peak" , "Peak, vertex" , "Topmost point" .)