Coat put on first of all (5)
I believe the answer is:
parka
'coat' is the definition.
(I know that parka is a type of coat)
'put on first of all' is the wordplay.
I cannot really see how this works, but
'put' could be 'park' (parking is a kind of putting) and 'park' is present in the answer.
'first' could be 'a' (first letter of the alphabet) and 'a' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for parka that I've seen before include "Kind of heavy jacket" , "Hooded warm jacket" , "Hooded garment" , "Short, hooded coat" , "hoodie" .)