Volunteers to get poet a jacket (6)
I believe the answer is:
tabard
'a jacket' is the definition.
(I've seen this before)
'volunteers to get poet' is the wordplay.
'volunteers' becomes 'TA' (abbreviation for Territorial Army).
'to get' says to put letters next to each other.
'poet' becomes 'bard' (bard is a kind of poet).
'ta'+'bard'='TABARD'
(Other definitions for tabard that I've seen before include "Sleeveless jerkin" , "Coat worn by herald" , "Jacket worn by a herald" , "Gilet" , "Knight's outer tunic" .)