Controls the market at street junctions (7)
I believe the answer is:
corners
This might be a double definition.
'controls the market' is the first definition.
'corners' can be an answer for 'controls' (cornering is a kind of controlling). I'm not certain of the 'the market' bit.
'street junctions' is the second definition.
'corners' can be an answer for 'junctions' (corner is a kind of junction). I am not certain of the 'street' bit.
'at' acts as a link.
Can you help me to learn more?
(Other definitions for corners that I've seen before include "Places where sides meet" , "Points where two lines meet" , "Where lines meet to form angles" , "Nooks" , "Where lines meet or intersect" .)