Shred the first thirteen letters (4)
I believe the answer is:
atom
'shred' is the definition.
(I've seen this in another clue)
'first thirteen letters' is the wordplay.
'first' becomes 'a' (first letter of the alphabet).
'thirteen letters' becomes 'tom' (I can't justify this - if you can you should believe this answer much more).
'a'+'tom'='ATOM'
'the' is the link.
Can you help me to learn more?
(Other definitions for atom that I've seen before include "Smallest unit of matter" , "It was once thought to be smallest particle of matter" , "Elementary particle" , "Very small bit" , "An explosive particle as in bomb" .)