Principal thoroughfare terminates oddly (4,6)
I believe the answer is:
main street
'principal thoroughfare' is the definition.
'main street' can be an answer for 'thoroughfare' (main street is a kind of thoroughfare). I'm not certain of the 'principal' bit.
'terminates oddly' is the wordplay.
'oddly' is an anagram indicator (letters in an odd order).
'terminates' with letters rearranged gives 'MAIN STREET'.
Can you help me to learn more?
(Other definitions for main street that I've seen before include "that divides many communities" , "American novel" .)