Sewer, lake and river up in northeast (6)
I believe the answer is:
needle
'sewer' is the definition.
(I've seen this before)
'lake and river up in north-east' is the wordplay.
'lake' becomes 'L' (geographical abbreviation).
'and' means one lot of letters go next to another.
'river up' becomes 'eed' (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.
'north east' becomes 'ne'.
'l' after 'eed' is 'eedl'.
'eedl' going into 'ne' is 'NEEDLE'.
Can you help me to learn more?
(Other definitions for needle that I've seen before include "Hostility - annoy - sewing tool" , "spur" , "Continually annoy" , "Cleopatra's" , "Annoy - syringe" .)