The most common and most likely answer to this crossword clue is the 6 letter word PAMPAS
I've seen this crossword clue in Independent
P
A
M
P
A
S
More clues leading to the result PAMPAS
- Plain girl father initially supported
- More than one plain maiden pops round
- Dad’s outside initially mowing the grass
- Pets barked in long grass
- Undermine plan to return Argentine parts
- Plain fool with plan drawn up
- Old man’s covering miles in vast plains
- It’s plain: Dad’s taking my half
- Father's destroying spam, it’s plain
- Dad’s enclosing Mom’s front areas of grass
Buddy explains!

The straight part
We know that "grass" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case grass = pampas.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 PAMPAS mean?
PAMPAS noun- The extensive plains of South America south of the Amazon.