The most common and most likely answer to this crossword clue is the 10 letter word DOWNMARKET
I've seen this crossword clue in The Daily Telegraph
D
O
W
N
M
A
R
K
E
T
More clues leading to the result DOWNMARKET
Buddy explains!

The straight part
We know that "Budget" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case budget = downmarket.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 DOWNMARKET mean?
DOWNMARKET verb- To make or become downmarket.
- Designed for low-income consumers.
- Of, or relating to the less prestigious sector of the market.
- Towards the less prestigious sector of the market.