Is one of these attached for part postage? (4)
I believe the answer is:
tags
'is' is the definition.
Although both the answer and definition are verbs in their -s form, I don't understand how they can define each other.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for tags that I've seen before include "They are able to identify" , "trite Latin quotations" , "Labels; quotations" .)