Stress caused by cooking pies and mash (8)
I believe the answer is:
emphasis
'stress' is the definition.
(synonyms)
'cooking pies and mash' is the wordplay.
'cooking' indicates anagramming the letters (cook can mean to falsify or distort).
'and' is a charade indicator (letters next to each other) (I've seen this in other clues).
'pies' after 'mash' is 'mashpies'.
'mashpies' is an anagram of 'EMPHASIS'.
'caused by' is the link.
(Other definitions for emphasis that I've seen before include "Stress, accentuation" , "Stress, accent" , "Accentutation" , "Special importance or prominence given to something" , "Force" .)