Meal to host a debut (6)
I believe the answer is:
launch
'debut' is the definition.
(thesaurus)
'meal to host a' is the wordplay.
'meal' becomes 'lunch' (lunch is a kind of meal).
'to host' means one lot of letters goes inside another (inserted letters are hosted or welcomed).
'lunch' going around 'a' is 'LAUNCH'.
(Other definitions for launch that I've seen before include "'Send into water or into space, say (6)'" , "Begin (a project)" , "Send off (a missile)" , "Of ship, formally set afloat" , "Fire (a rocket)" .)