Pooch barking grabs new garment (6)
I believe the answer is:
poncho
'garment' is the definition.
(poncho is a kind of garment)
'pooch barking grabs new' is the wordplay.
'barking' indicates an anagram (UK slang for mad).
'grabs' is an insertion indicator.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'pooch' anagrammed gives 'pocho'.
'pocho' enclosing 'n' is 'PONCHO'.
(Other definitions for poncho that I've seen before include "Latin American-style cloak" , "Garment with slit for the head" , "Blanket-like cloth with centre slit, worn as cloak" , "Overgarment with hole for head" , "Blanket-style cloak" .)