Agreement to include old Poles in survey (9)
I believe the answer is:
consensus
'agreement' is the definition.
(I know that consensus is a type of agreement)
'to include old poles in survey' is the wordplay.
'to include' indicates putting letters inside.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'poles' becomes 'NS' (North and South poles).
'in' means one lot of letters goes inside another.
'survey' becomes 'census' (I've seen this before).
'ns' put into 'census' is 'cnsensus'.
'o' put inside 'cnsensus' is 'CONSENSUS'.
(Other definitions for consensus that I've seen before include "General opinion" , "agreed" , "Unanimity" , "Majority view" , "General agreement" .)