Drinks round after round (4)
I believe the answer is:
laps
'drinks' is the definition.
(lapping is a kind of drinking)
'round after round' is the wordplay.
'round' becomes 'lap' (as in a round or lap of a park).
'after round' becomes 's' (I can't justify this - if you can you should give a lot more credence to this answer).
'lap'+'s'='LAPS'
Can you help me to learn more?
(Other definitions for laps that I've seen before include "Drinks; circuits" , "Circuits of a racetrack" , "Pals doing rounds of the track" , "Scoops up with the tongue" , "Circuits of track" .)