This month, everything's put in place (7)
'put in place' is the definition.
'this month everything's' is the wordplay.
'this month' becomes 'inst' (I've seen this before).
'everything' becomes 'all' (I've seen this before).
(Other definitions for install that I've seen before include "Station", "Put in - invest", "Put in place ready for use", "Load up", "Fix in position ready for use".)