Everyone with us on about one reference (8)
I believe the answer is:
allusion
'reference' is the definition.
(I know that allusion is a type of reference)
'everyone with us on about one' is the wordplay.
'everyone' becomes 'all' (all people).
'with' is a charade indicator (letters next to each other).
'about' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'on' put after 'i' is 'ion'.
'us' next to 'ion' is 'usion'.
'all'+'usion'='ALLUSION'
(Other definitions for allusion that I've seen before include "Passing reference or indirect mention" , "A brief or indirect reference to something" , "Subtle reference" .)