Unusually impulsive VIP missing breakfast? (6)
I believe the answer is:
muesli
'breakfast?' is the definition.
(common breakfast food)
'unusually impulsive vip missing' is the wordplay.
'unusually' indicates an anagram.
'missing' is a deletion indicator.
'impulsive' with 'vip' taken out is 'mulsie'.
'mulsie' is an anagram of 'MUESLI'.
(Other definitions for muesli that I've seen before include "Breakfast dish of cereal, dried fruit and nuts in milk" , "Breakfast food of cereals, dried fruit, nuts etc" , "Oat-based breakfast cereal" , "Mixture of crushed cereals. nuts and fruit" , "eaten at breakfast" .)