Purchase eagerly and quickly (4,2)
I believe the answer is:
snap up
'purchase eagerly and quickly' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for snap up that I've seen before include "Quickly accept" , "Snatch" , "Purchase eagerly and quickly" , "Grab eagerly and quickly" , "Buy (a rarity) quickly" .)