Poles dividing it all to invest in office (7)
I believe the answer is:
install
'invest in office' is the definition.
(as in installing someone in a post)
'poles dividing it all' is the wordplay.
'poles' becomes 'ns' (North and South poles).
'dividing' means one lot of letters goes inside another (inserted letters divide the word).
'ns' going inside 'it' is 'inst'.
'inst'+'all'='INSTALL'
'to' acts as a link.
(Other definitions for install that I've seen before include "Set up, ready for use" , "Place in position, establish" , "Set in place" , "put in office" , "Put in place ready for use" .)