General agreement count of people must include acceptable syntax at outset (9)
I believe the answer is:
consensus
'general agreement' is the definition.
(synonyms)
'count of people must include acceptable syntax at outset' is the wordplay.
'count of people' becomes 'census' (I've seen this before).
'must include' indicates putting letters inside.
'acceptable' becomes 'on' (as opposed to not on, unacceptable).
'at outset' says to take the initial letters.
The initial letter of 'syntax' is 's'.
'on'+'s'='ons'
'census' going around 'ons' is 'CONSENSUS'.
(Other definitions for consensus that I've seen before include "Majority view" , "Unanimity" , "General agreement" , "agreed" , "General opinion" .)