Herald's coat, thanks to Shakespeare! (6)
I believe the answer is:
tabard
'herald's coat' is the definition.
(I've seen this before)
'thanks to shakespeare' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'to shakespeare' becomes 'bard' (Shakespeare is known as the Bard).
'ta'+'bard'='TABARD'
(Other definitions for tabard that I've seen before include "Sleeveless jerkin" , "Herald's jacket" , "Jerkin; heraldic coat" , "Short sleeveless tunic" , "Clobber" .)