Formula One champion's girl's from South (5)
I believe the answer is:
senna
'formula one champion's' is the definition.
(racing driver Ayrton Senna)
'girl's from south' is the wordplay.
'girl's' becomes 'Anne's' (girl's name).
'from south' says the letters should be written in reverse.
'annes' back-to-front is 'SENNA'.
(Other definitions for senna that I've seen before include "Cassia tree, laxative" , "should make you want to go quickly" , "Tropical plant with medicinal leaflets" , "taking this to speed up motion?" , "given help to get in motion?" .)