Negligible (5)
(Other definitions for scant that I've seen before include "In short supply" , "Deficient, sparing" , "Barely adequate" , "Reduce" , "Less than the required amount" .)
(Other definitions for mere that I've seen before include "Insignificant" , "Pond - pure and simple" , "Just an English lake" , "Bare, simple" , "Lake; Wiltshire town" .)
'negligible' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for slim that I've seen before include "Thin (person); small (chance)" , "Bakery produce" , "insufficient" , "Lean" , "Gracefully thin" .)