In certain parts, this is out of the way (6)
I believe the answer is:
thirds
'in certain parts' is the definition.
'thirds' can be an answer for 'parts'. I am not certain of the 'in certain' bit.
'this is out of the way' is the wordplay.
'is out of' indicates putting letters inside (some letters on the outside of others).
'the way' becomes 'rd' (short for road).
'this' enclosing 'rd' is 'THIRDS'.
Can you help me to learn more?
(Other definitions for thirds that I've seen before include "Degrees" , "sections" , "Three equal parts" , "Musical intervals" .)