Friends suggested such a celebratory meal? (4-2)
I believe the answer is:
slap-up
'such a celebratory meal?' is the definition.
(as in a slap-up meal)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for slap-up that I've seen before include "Luxurious (feast)" , "This meal is first-class" , "With no expense spared" , "Lavish, meal say" , "(Of meal) large/lavish" .)