Good Friday fare inflamed crabby posterior (3,5,4)
I believe the answer is:
hot cross buns
'good friday fare' is the definition.
(I've seen this before)
'inflamed crabby posterior' is the wordplay.
'inflamed' becomes 'hot'.
'crabby' becomes 'cross' (synonyms).
'posterior' becomes 'buns' (synonyms).
'hot'+'cross'+'buns'='HOT CROSS BUNS'
(Other definitions for hot cross buns that I've seen before include "Good Friday fare" , "Bank holiday fare" , "They're traditionally eaten on Good Friday" , "Easter specialities" .)