The most common and most likely answer to this crossword clue is the 4 plus 2 letter word PASS UP
I've seen this crossword clue in The Times
P
A
S
S
U
P
More clues leading to the result PASS UP
- Refuse amorous advance at university
- 5 dads drink
- Have nothing to do with free ticket winning
- Don’t take advantage of fool knocking back drink
- Don’t take opportunity to succeed at university
- Ignore young setter perhaps inhaling dope
- Take no notice of idiot little dog bites
- Turn down conceited youngster, idiot needing introduction
- Let go by Bottom after pressure to get out of bed
- Cat keeled over after father let go
Buddy explains!

The straight part
We know that "refuse" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case refuse = pass up.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.