Queen avoiding area linked to unknown highway (6)
I believe the answer is:
artery
'highway' is the definition.
(artery can mean a major road)
'queen avoiding area linked to unknown' is the wordplay.
'queen' becomes 'r' (abbreviation for regina, e.g. in ER ).
'avoiding area' becomes 'arte' (I can't justify this - if you can you should believe this answer much more).
'linked to' means one lot of letters go next to another.
'unknown' becomes 'y' (algebra).
'r' put after 'arte' is 'arter'.
'arter'+'y'='ARTERY'
(Other definitions for artery that I've seen before include "Major (blood) route" , "bloody path" , "vital route" , "Principle channel of circulatory system" , "vessel carrying vital supply" .)