Very small quantity (7)
'very small quantity' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for soupcon that I've seen before include "suspicion" , "Small amount of food" , "A very small quantity, from French" , "Very tiny amount" , "Dash" .)
(Other definitions for handful that I've seen before include "Nuisance - not a lot" , "Someone hard to control" , "Perhaps lively child" , "Something hard to control - small number" , "Smattering" .)