He might deliver latest in the Dow Jones branch office in the City (7)
I believe the answer is:
newsboy
'he might deliver' is the definition.
(someone delivering newspapers)
'latest in the dow jones branch office in the city' is the wordplay.
'latest in' indicates one should take the final letters.
'branch office' becomes 'BO' (business abbreviation).
'in' means one lot of letters goes inside another.
'the city' becomes 'ny' (New York city).
The last letters of 'the dow jones' are 'ews'.
'ews'+'bo'='ewsbo'
'ewsbo' placed within 'ny' is 'NEWSBOY'.
(Other definitions for newsboy that I've seen before include "Delivering lad" , "Paper deliverer" .)