Pick-me-up, usually after gin (5)
I believe the answer is:
tonic
'pick-me-up' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for tonic that I've seen before include "Producing tension of muscles" , "something invigorating" , "Keynote of a scale" , "Invigorating liquid" , "do for musicians" .)