Silicate almost cracks, showing signs of stress (7)
I believe the answer is:
italics
'signs of stress' is the definition.
(italics are used to stress or emphasise text)
'silicate almost cracks' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'cracks' is an anagram indicator (I've seen 'cracked' mean this).
'silicate' with its final letter taken off is 'silicat'.
'silicat' with letters rearranged gives 'ITALICS'.
'showing' is the link.
(Other definitions for italics that I've seen before include "Typeface with letters slanting to the right" , "Sloping text" , "indication of stress?" , "Sloping typeface" , "Letters slanting upward to the right" .)