Dessert granny's put in bread roll and set fire to (6,5)
I believe the answer is:
banana split
'dessert' is the definition.
(banana split is a kind of dessert)
'granny's put in bread roll and set fire to' is the wordplay.
'granny's' becomes 'nana's' (both can mean a grandmother).
'put in' indicates putting letters inside.
'bread roll' becomes 'bap' (bap can mean a roll).
'and' means one lot of letters go next to another.
'set fire to' becomes 'lit' (as in lighting a fire).
'nanas' inserted into 'bap' is 'bananasp'.
'bananasp'+'lit'='BANANA SPLIT'
(Other definitions for banana split that I've seen before include "Fruit and ice cream dessert" , "sweet food" , "Ice-cream dish" , "Ice cream dish" .)