A second coffee maybe (7)
I believe the answer is:
instant
'a second' is the definition.
(I know that instant is a type of second)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for instant that I've seen before include "Jiffy" , "Immediate; moment in time" , "pressing" , "Occurring with no delay" , "Mo" .)