VIP giving one a broad grin! (3,6)
I believe the answer is:
big cheese
'vip' is the definition.
(I've seen this before)
'giving one a broad grin' is the wordplay.
'giving' becomes 'big' (synonyms).
'one a broad grin' becomes 'cheese' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'big'+'cheese'='BIG CHEESE'
Can you help me to learn more?
(Other definitions for big cheese that I've seen before include "Mousetrap attraction!" , "Important chap" , "Important person (slang)" , "boss" , "Large cake of Cheshire, perhaps" .)