Decorated parts of large garden, fencing apart (9)
I believe the answer is:
paintwork
'decorated parts of large' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'garden fencing apart' is the wordplay.
'garden' becomes 'park' (I have seen 'Public garden ' mean 'park' so perhaps 'garden' could also mean 'park').
'fencing' means one lot of letters goes inside another (to fence can mean to contain or put a limit round).
'apart' becomes 'in two' (as in 'split in two').
'park' enclosing 'intwo' is 'PAINTWORK'.
Can you help me to learn more?
(Other definitions for paintwork that I've seen before include "Decoration" , "Coats maybe" , "matt and gloss?" .)