Cast breaks up for short meal (4,3)
I believe the answer is:
spag bol
'short meal' is the definition.
(short for spaghetti Bolognese; 'short' indicates an abbreviation)
'cast breaks up' is the wordplay.
'cast' becomes 'lob'.
'breaks' becomes 'gaps' ('gap' can be a synonym of 'break').
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'lob'+'gaps'='lobgaps'
'lobgaps' back-to-front is 'SPAG BOL'.
'for' is the link.
(Another definition for spag bol that I've seen is " Simple meat and pasta dish (abbr)".)