Rhyme about milk and rice (8)
I believe the answer is:
limerick
'rhyme' is the definition.
(I know that limerick is a type of rhyme)
'about milk and rice' is the wordplay.
'about' is an anagram indicator.
'and' says to put letters next to each other.
'milk' put after 'rice' is 'ricemilk'.
'ricemilk' anagrammed gives 'LIMERICK'.
(Other definitions for limerick that I've seen before include "Humorous poem from the Treaty City?" , "Humorous short poem" , "Type of humorous verse" , "Irish county's produced" , "port used in Ireland" .)