Tip making primate cross (4)
I believe the answer is:
apex
'tip' is the definition.
(I've seen this before)
'primate cross' is the wordplay.
'primate' becomes 'ape' (large primate).
'cross' becomes 'x' (X is cross-shaped).
'ape'+'x'='APEX'
'making' acts as a link.
(Other definitions for apex that I've seen before include "The highest point or peak" , "Cheap fare" , "Uppermost tip" , "Top, peak" , "Top, highest part" .)