Coat available in various colours (5)
I believe the answer is:
paint
'coat' is the definition.
(paint is a kind of coat)
'available in various colours' is the wordplay.
'available' becomes 'in' (I've seen this in other clues).
'in' is an insertion indicator.
'various colours' becomes 'pat' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' put into 'pat' is 'PAINT'.
Can you help me to learn more?
(Other definitions for paint that I've seen before include "Colouring matter for decoration" , "Eg, emulsion or gloss" , "Decorative coating" , "Surface coating or decoration" , "A pint of liquid decoration" .)