Pick-me-up, often after a gin (5)
I believe the answer is:
tonic
'pick-me-up' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for tonic that I've seen before include "Stimulant" , "A pick-me-up drink, nice with gin" , "Accompaniment to gin?" , "Important note" , "that may be mixed with gin" .)