The most common and most likely answer to this crossword clue is the 6 letter word UPTICK
U
P
T
I
C
K
Buddy explains!
The straight part
We know that "Increase" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case increase = uptick.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 UPTICK mean?
UPTICK noun- A small increase or upward change in something that has been steady or declining.
- A stock market transaction or quote at a price above a preceding one.