Dad finds humour in sweet treat (7)
I believe the answer is:
popcorn
'treat' is the definition.
The definition and answer can be both things that one consumes for nourishment as well as being singular nouns.
Maybe there's an association between them I don't understand?
'dad finds humour in sweet' is the wordplay.
'dad' becomes 'pop' (synonyms).
'finds' says to put letters next to each other.
'humour in sweet' becomes 'corn' (I am not sure about this - if you are sure you should believe this answer much more).
'pop'+'corn'='POPCORN'
Can you help me to learn more?
(Other definitions for popcorn that I've seen before include "Kernels exploded by heat" , "Maize heated into crisp edible balls, often eaten in cinema" , "Exploded maize" , "Stuff to eat at the cinema" , "Feature accompaniment" .)