Undergarments are hits (5)
I believe the answer is:
socks
This clue could be a double definition.
'undergarments' is the first definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Maybe they are linked in a way I don't understand?
'are hits' is the second definition.
Can you help me to learn more?
(Other definitions for socks that I've seen before include "Foot garments" , "Are belts" , "Items of hosiery" , "Hits forcefully, garments" , "Disappointment at Xmas" .)