Soften everything one included in paste (8)
I believe the answer is:
palliate
'soften' is the definition.
(thesaurus)
'everything one included in paste' is the wordplay.
'everything' becomes 'all' (I've seen this before).
'one' becomes 'i' (Roman numeral).
'included in' indicates putting letters inside.
'paste' becomes 'pate' (pate is a kind of paste).
'all'+'i'='alli'
'alli' placed within 'pate' is 'PALLIATE'.
(Other definitions for palliate that I've seen before include "everything before I cut into spread" , "Allay" , "Eat a pill (anag) - make easier" , "Soften (the effect of)" , "Mitigate (something bad)" .)