The most common and most likely answer to this crossword clue is the 6 letter word KEENER
I've seen this crossword clue in Financial Times
K
E
E
N
E
R
Buddy explains!

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 KEENER mean?
KEENER adjective- Often with a prepositional phrase, or with to and an infinitive: showing a quick and ardent responsiveness or willingness; eager, enthusiastic, interested.
- Fierce, intense, vehement.
- Having a fine edge or point; sharp.
- Acute of mind, having or expressing mental acuteness; penetrating, sharp.
- Acrimonious, bitter, piercing.
- Of cold, wind, etc.: cutting, penetrating, piercing, sharp.
- Of prices, extremely low as to be competitive.
- Marvelous.
- Brave, courageous; audacious, bold.
- One who keens at a funeral.
- Someone who is excessively keen or eager, possibly making others look bad; a brown-noser.