Weight of pies and mash demolished (8)
I believe the answer is:
emphasis
'weight' is the definition.
(thesaurus)
'pies and mash demolished' is the wordplay.
'and' is a charade indicator (letters next to each other).
'demolished' indicates anagramming the letters.
'pies'+'mash'='piesmash'
'piesmash' with letters rearranged gives 'EMPHASIS'.
'of' acts as a link.
(Other definitions for emphasis that I've seen before include "Importance; priority" , "Stress, accentuation" , "Force" , "Accentutation" , "Stress laid on, eg, words" .)