Thanks Eisteddfod winner for tunic (6)
I believe the answer is:
tabard
'tunic' is the definition.
(tabard is a kind of tunic)
'thanks eisteddfod winner' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'eisteddfod winner' becomes 'bard' (I've seen this before).
'ta'+'bard'='TABARD'
'for' is the link.
(Other definitions for tabard that I've seen before include "Sleeveless jacket" , "Jerkin; heraldic coat" , "[A] top" , "Herald's jacket" , "Clobber" .)