Father Arena acquired coat (6)
I believe the answer is:
patina
'acquired coat' is the definition.
'patina' can be an answer for 'coat' (patina is a kind of coat). I'm not sure about the 'acquired' bit.
'father arena' is the wordplay.
'father' becomes 'pa' (pa can mean dad or father).
'arena' becomes 'tina' (I am not sure about this - if you are sure you should believe this answer much more).
'pa'+'tina'='PATINA'
Can you help me to learn more?
(Other definitions for patina that I've seen before include "A surface gloss produced by age" , "Surface film formed by age" , "Green coating on bronze" , "Green gloss on old bronze" , "Surface coating that comes with age" .)