Small quantity (7)
'small quantity' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for modicum that I've seen before include "Moderate quantity" , "I cod Mum into providing a small quantity" , "A small amount as of drink" , "A small portion" , "dash" .)
(Other definitions for handful that I've seen before include "Someone hard to control" , "children that are difficult to control" , "Small number or amount" , "Something hard to control - small number" , "Small number - difficult person or thing" .)