1. a small amount
handful of sweets/people/
A 'handful' can refer to a small amount of something. A 'handful' can refer to an amount or quantity of something that can fit in the palm of your hand. 'Only a handful of people came to the talk yesterday.' 'I just have a handful of days off left this year.'
2. difficult to control, misbehaved
the child was a handful to deal with
A 'handful' is an adjective used to describe a situation or individual which is impossible or very difficult to manage or control. The image here is of someone having their hands full with tasks in order to manage a situation.