Leather whip shortly for breaking rules (7)
I believe the answer is:
cowhide
'leather' is the definition.
(I know that cowhide is a type of leather)
'whip shortly for breaking rules' is the wordplay.
'shortly' means to remove the last letter.
'for breaking' means one lot of letters goes inside another (inserted letters break into the word).
'rules' becomes 'code'.
'whip' with its final letter taken away is 'whi'.
'whi' going into 'code' is 'COWHIDE'.
(Other definitions for cowhide that I've seen before include "Type of leather" , "Giving leather" , "whip" , "neat wrapper?" .)