Mock regulation restricting DI back in charge (8)
I believe the answer is:
ridicule
'mock' is the definition.
(ridiculing is a kind of mocking)
'regulation restricting di back in charge' is the wordplay.
'regulation' becomes 'rule' ('rule' can be a synonym of 'regulation').
'restricting' indicates putting letters inside.
'back' shows that the letters should be reversed in order.
'in charge' becomes 'ic'.
'di' reversed gives 'id'.
'id'+'ic'='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" , "satire" , "Subjection to mockery and derision" .)