Significant dates that could make insane sir rave (13)
I believe the answer is:
anniversaries
'significant dates' is the definition.
(I've seen this before)
'could make insane sir rave' is the wordplay.
'could make' is an anagram indicator.
'insane'+'sir'+'rave'='insanesirrave'
'insanesirrave' with letters rearranged gives 'ANNIVERSARIES'.
'that' is the link.
(Other definitions for anniversaries that I've seen before include "Significant dates" , "occasions" .)