The part of the knickers that gets us in a twist? (6)
I believe the answer is:
gusset
'the part' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'the knickers that gets us in a twist?' is the wordplay.
'gets us' anagrams to 'GUSSET'.
But, I'm not clear how the anagram is indicated.
'of' is the link.
Can you help me to learn more?
(Other definitions for gusset that I've seen before include "Gets us (anag.)" , "Piece of material set into a dress" , "Strengthening material insert" , "Strengthening piece of fabric" , "Piece inserted to strengthen or enlarge a garment" .)