Mock regulation that includes single endless edict (8)
I believe the answer is:
ridicule
'mock' is the definition.
(ridiculing is a kind of mocking)
'regulation that includes single endless edict' is the wordplay.
'regulation' becomes 'rule' (synonyms).
'that includes' is an insertion indicator.
'single' becomes 'I' (one).
'endless' means to look at the middle letters.
The centre of 'edict' is 'dic'.
'i'+'dic'='idic'
'rule' placed around 'idic' is 'RIDICULE'.
(Other definitions for ridicule that I've seen before include "Laugh at or deride" , "I rid clue of derision" , "guy" , "Mock, make fun of." , "satire" .)