Accent on giving best start to rascal (6)
I believe the answer is:
brogue
'accent' is the definition.
(brogue can mean a Scottish or Irish accent)
'giving best start to rascal' is the wordplay.
'giving' is a charade indicator (letters next to each other).
'start to' suggests taking the first letters.
'rascal' becomes 'rogue' (both can mean a scoundrel).
The first letter of 'best' is 'b'.
'b'+'rogue' is 'BROGUE'.
'on' acts as a link.
(Other definitions for brogue that I've seen before include "Stout leather shoe" , "Thick and heavy shoe" , "Worn" , "Outdoor shoe; accent" , "Irish or Scottish accent?" .)