Work is terrible, to a peer (7)
I believe the answer is:
operate
'work' is the definition.
(I know that work can be written as operate)
'terrible to a peer' is the wordplay.
'terrible' indicates an anagram.
'to'+'a'+'peer'='toapeer'
'toapeer' with letters rearranged gives 'OPERATE'.
'is' acts as a link.
(Other definitions for operate that I've seen before include "Act in a theatre" , "Cut - run" , "Manage, run" , "Work, function" , "Control, run, a mcahine say" .)