The most common and most likely answer to this crossword clue is the 6 letter word DEARER
I've seen this crossword clue in Independent
D
E
A
R
E
R
Buddy explains!

The straight part
We know that "more expensive" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case more expensive = dearer.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 DEARER mean?
DEARER adjective- High in price; expensive.
- Loved; lovable.
- Loving, affectionate, heartfelt
- Precious to or greatly valued by someone.
- A formal way to start (possibly after my) addressing somebody at the beginning of a letter, memo etc.
- A formal way to start (often after my) addressing somebody one likes or regards kindly.
- An ironic way to start (often after my) addressing an inferior.
- Noble.