Antiseptics pioneer takes in northeast one hears (8)
I believe the answer is:
listener
'one hears' is the definition.
(I've seen this before)
'antiseptics pioneer takes in northeast' is the wordplay.
'antiseptics pioneer' becomes 'Lister' (Joseph Lister pioneered antiseptic surgery).
'takes in' means one lot of letters goes inside another.
'northeast' becomes 'NE' (abbreviation).
'lister' placed around 'ne' is 'LISTENER'.
(Other definitions for listener that I've seen before include "One lending an ear" , "Auditor" , "One paying attention" , "Radio fan" , "One attending" .)