To work at home is murder (2,2)
I believe the answer is:
do in
'is murder' is the definition.
(thesaurus)
'to work at home' is the wordplay.
'to work' becomes 'do' ('do work' can be a synonym of 'work'**).
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'do'+'in'='DO IN'
(Other definitions for do in that I've seen before include "Knock off" , "Get rid of" , "Murder" .)