Small child's bit of money (4)
I believe the answer is:
mite
This clue might be a double definition.
'small child's' is the first definition.
(informal term)
'bit of money' is the second definition.
'mite' can be an answer for 'bit' (I've seen this in another clue). I'm unsure of the 'of money' bit.
Can you help me to learn more?
(Other definitions for mite that I've seen before include "Tiny contribution, child" , "Old piece" , "Tiny creature found in food" , "Child; a small amount" , "The widow's contribution, just in time" .)