Small number that's hard to manage (7)
I believe the answer is:
handful
'small number' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for handful that I've seen before include "Someone hard to control" , "Small number - difficult person or thing" , "Perhaps lively child" , "Small number or amount" , "'Small number, a fistful (7)'" .)