Concern with bus in Essex dropping last two off (8)
I believe the answer is:
business
'essex dropping last two off' is the definition.
I can't tell whether this defines the answer.
'concern with bus in' is the wordplay.
'concern with' becomes 'sines' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'sines' inserted within 'bus' is 'BUSINESS'.
(Other definitions for business that I've seen before include "Concern; commerce" , "outfit" , "Profession - trade - matter" , "Work - shop" , "Occupation; concern" .)