The most common and most likely answer to this crossword clue is the 9 letter word ROLY-POLY
I've seen this crossword clue in Financial Times
R
O
L
Y
-
P
O
L
Y
More clues leading to the result ROLY-POLY
Buddy explains!

The straight part
We know that "Plump/pudding" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plump/pudding = roly-poly.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 ROLY-POLY mean?
ROLY-POLY noun- A short, plump person.
- A steamed pudding made from suet pastry containing jam or fruit.
- A forward roll or sideways roll.
- A terrestrial crustacean of suborder Oniscidea; pill bug, potato bug or sowbug.
- A toy that rights itself when pushed over.
- An old game in which balls are bowled into holes or thrown into hats placed on the ground.
- Short and plump.
- Moving with a roll and sway.
- By rolling, so as to roll.
- Directly, without hesitating.