Smash pie out of stress (8)
I believe the answer is:
emphasis
'stress' is the definition.
(synonyms)
'smash pie out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'smash'+'pie'='smashpie'
'smashpie' anagrammed gives 'EMPHASIS'.
'of' is the link.
(Other definitions for emphasis that I've seen before include "Accentutation" , "Stress - misshape (anag)" , "Force" , "Special importance or prominence given to something" , "Importance; priority" .)