The main thing holding papers together? (6)
I believe the answer is:
staple
'the main' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for staple that I've seen before include "Clip" , "Fastening wire" , "Basic commodity and paper fastener" , "Pleats in a paper pin" , "office item" .)