If you want a drink, move fast (3)
I believe the answer is:
nip
'drink move fast' is the definition.
'nip' can be an answer for 'drink' (I've seen this before). I am not certain of the 'move fast' bit.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for nip that I've seen before include "(Give) a small sharp bite" , "Light bite" , "Touch of frost" , "Pinch; bite" , "Quick, sharp, bite" .)