US city's way to divide benefit (6)
I believe the answer is:
boston
'us city's' is the definition.
(capital of Massachusetts)
'way to divide benefit' is the wordplay.
'way' becomes 'st' (abbreviation for street).
'to divide' is an insertion indicator (some letters create a division in others).
'benefit' becomes 'boon' (I've seen this before).
'st' inserted inside 'boon' is 'BOSTON'.
(Other definitions for boston that I've seen before include "US city; card game" , "Site of rebellious tea party" , "where tea was spilt" , "Card game; dance" , "US city of historic Tea Party" .)