Initially take away drop: a small amount (3)
I believe the answer is:
tad
'a small amount' is the definition.
(I've seen this before)
'initially take away drop' is the wordplay.
'initially' suggests taking the first letters.
The initial letters of 'take away drop' is 'TAD'.
(Other definitions for tad that I've seen before include "little boy" , "(A) bit, touch" , "Small bit" , "Modest amount" , "A small amount (colloq.)" .)