Favour girl, teetotaller, with energy (7)
I believe the answer is:
rosette
'favour' is the definition.
('favour' historically meant a token of affection)
'girl teetotaller with energy' is the wordplay.
'girl' becomes 'rose' (**).
'teetotaller' becomes 'tt' (abbreviation).
'with' says to put letters next to each other.
'energy' becomes 'e' (physics symbol as in E=mco).
'rose'+'tt'+'e'='ROSETTE'
(Other definitions for rosette that I've seen before include "Cockade" , "Colourful decoration worn by supporters" , "Prize; favour" , "Ribbon badge for prize-winner" , "Ribboned decoration" .)