Youngster of frugality (3)
I believe the answer is:
gal
'youngster' is the definition.
'of frugality' is the wordplay.
'of' says the answer is hidden in the clue.
'GAL' is hidden in the letters of 'frugality'.
(Other definitions for gal that I've seen before include "US female" , "measure of acceleration?" , "female noted in Kalamazoo" , "Girl from American west" , "Young woman (colloq.)" .)