Monarchy initially collapsed, worn out (5)
I believe the answer is:
crown
'monarchy' is the definition.
'initially collapsed worn out' is the wordplay.
'initially' says to take the initial letters.
'out' is an anagram indicator (out can mean wrong or inaccurate).
The first letter of 'collapsed' is 'c'.
'worn' with letters rearranged gives 'rown'.
'c'+'rown'='CROWN'
(Other definitions for crown that I've seen before include "Royal headdress" , "King" , "Visible part of a tooth" , "Coronet" , "Summit" .)