The most common and most likely answer to this crossword clue is the 13 letter word SMALLHOLDINGS
I've seen this crossword clue in The Guardian
S
M
A
L
L
H
O
L
D
I
N
G
S
More clues leading to the result SMALLHOLDINGS
Buddy explains!

The straight part
We know that "farms" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case farms = smallholdings.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 SMALLHOLDINGS mean?
SMALLHOLDINGS noun- A piece of land, smaller than a farm, used for the cultivation of vegetables or the breeding of animals.
- A small plantation or land with a small number of slaves (generally 19 or less). Contrasted with middling plantation (20-49 slaves) and large plantation (50+ and owned by planters).