The most common and most likely answer to this crossword clue is the 9 letter word VARNISHES
I've seen this crossword clue in The Daily Telegraph
V
A
R
N
I
S
H
E
S
Buddy explains!

The straight part
We know that "Puts on coat perhaps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case puts on coat perhaps = varnishes.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does VARNISHES mean?
VARNISHES noun- A type of paint with a solvent that evaporates to leave a hard, transparent, glossy film.
- Anything resembling such a paint; glossy appearance.
- (by extension) A deceptively showy appearance.
- A passenger train, probably derived from the varnished passenger cars used at one time.