Former PM's diaries edited to restrict length (8)
I believe the answer is:
disraeli
'former pm's' is the definition.
(I've seen this before)
'diaries edited to restrict length' is the wordplay.
'edited' indicates an anagram.
'to restrict' indicates putting letters inside.
'length' becomes 'l'.
'diaries' with letters rearranged gives 'disraei'.
'disraei' going around 'l' is 'DISRAELI'.
(Other definitions for disraeli that I've seen before include "Queen Victoria's favourite prime minister, d. 1881" , "Victorian PM" , "Benjamin --, former PM" , "One of Queen Victoria's prime ministers" , "Victorian prime minister" .)