Becomes zombie? Knickers! (6)
I believe the answer is:
undies
'knickers' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for undies that I've seen before include "Personal attire" , "Knickers (abbrev.)" , "clothing not normally seen" , "linen" , "Undergarments (colloq.)" .)