Veronica, healthy after drug (9)
I believe the answer is:
speedwell
'veronica' is the definition.
('speedwell' can be a synonym of 'veronica')
'healthy after drug' is the wordplay.
'healthy' becomes 'well' ('well' can be similar in meaning to 'healthy').
'after' is a charade indicator (letters next to each other).
'drug' becomes 'speed' (speed is a kind of drug**).
'well' put after 'speed' is 'SPEEDWELL'.
(Other definitions for speedwell that I've seen before include "Small blue flower of the genus veronica" , "Small creeping herbaceous plant with blue or pink flowers" , "bloomer?" , "Flowering plant" , "Small plant, veronica" .)