Times' first edition shows substance (6)
I believe the answer is:
tissue
'substance' is the definition.
(tissue is a kind of substance)
'times' first edition' is the wordplay.
'first' suggests taking the first letters.
'edition' becomes 'issue' (I've seen this before).
The initial letter of 'times' is 't'.
't'+'issue'='TISSUE'
'shows' is the link.
(Other definitions for tissue that I've seen before include "Flimsy paper" , "magazine?" , "See 17" , "Sneeze catcher?" , "used to make up lies?" .)