Small amount to give expert (3,4)
I believe the answer is:
dab hand
'expert' is the definition.
(I've seen this before)
'small amount to give' is the wordplay.
'small amount' becomes 'dab' (I've seen this before).
'to give' becomes 'hand' (synonyms).
'dab'+'hand'='DAB HAND'
(Other definitions for dab hand that I've seen before include "cursory wash?" , "Barely wash" , "An informal expert such as band had" , "Past master" .)