A sheep leaves and runs amok (8)
I believe the answer is:
rampages
'runs amok' is the definition.
(I've seen this in another clue)
'a sheep leaves' is the wordplay.
'a sheep' becomes 'ram' (male sheep).
'leaves' becomes 'pages' (leaf can mean a page).
'ram'+'pages'='RAMPAGES'
'and' is the link.
(Other definitions for rampages that I've seen before include "Violent and destructive behaviours" , "runs wild" , "Moves through a place in a violent and uncontrollable way" , "Violent disorders" , "Rushes around wildly" .)