Grand party-thrower has a bit of skinny people's leftovers? (6)
I believe the answer is:
ghosts
'people's leftovers?' is the definition.
(ghosts are people's spirits)
'grand party-thrower has a bit of skinny' is the wordplay.
'grand' becomes 'g' (G is short for grand as in a thousand).
'party thrower' becomes 'host' (someone hosting a party).
'has' says to put letters next to each other.
'a bit of' says to take the initial letters.
The first letter of 'skinny' is 's'.
'g'+'host'+'s'='GHOSTS'
(Other definitions for ghosts that I've seen before include "Writes for another; Ibsen play" , "Spirits or apparitions" , "Apparitions of a dead people" , "Spooks, spectres" , "Spectres, wraiths" .)