A second drink in student's pad (6)
I believe the answer is:
refill
This clue might be a double definition.
'a second drink' is the first definition.
(I've seen this in another clue)
'student's pad' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'in' is the link.
Can you help me to learn more?
(Other definitions for refill that I've seen before include "Charge again" , "Replace contents" , "Solution for dried-up writer" , "Another cuppa perhaps" , "Top up glass, replenish" .)