The most common and most likely answer to this crossword clue is the 11 letter word GREENHOUSES
I've seen this crossword clue in The Daily Telegraph
G
R
E
E
N
H
O
U
S
E
S
Buddy explains!
The straight part
We know that "They boost growth" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they boost growth = greenhouses.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 GREENHOUSES mean?
GREENHOUSES noun- A building used to grow plants, particularly one with large glass windows or plastic sheeting to trap heat from sunlight even in intemperate seasons or climates.
- The glass of a plane's cockpit.
- A structure that shields the operating table to protect against bacteria.
- A hot state in global climate.