Record times broken in one event's opening (7)
I believe the answer is:
itemise
'record' is the definition.
('record'->'itemize' is in my internal thesaurus and 'ize'->'ise')
'times broken in one event's opening' is the wordplay.
'broken' indicates an anagram.
'in' is an insertion indicator.
'one' becomes 'i' (Roman numeral**).
'opening' says to take the initial letters.
The first letter of 'events' is 'e'.
'times' is an anagram of 'temis'.
'i'+'e'='ie'
'temis' inserted inside 'ie' is 'ITEMISE'.
(Other definitions for itemise that I've seen before include "List in detail" , "List, state each object" , "List exhaustively" , "Using spell out" , "Formulate a list" .)