The most common and most likely answer to this crossword clue is the 6 letter word RARELY
I've seen this crossword clue in Independent
R
A
R
E
L
Y
More clues leading to the result RARELY
- Margins deserting Arab Bank? Not often!
- Hardly ever is gran’s meat lean
- Customer finally goes to a bank on very few occasions
- Annual return adopted by bank on only a few occasions
- Seldom depend on the Gunners
- Bloody lavatory emptied once in a blue moon
- A queen enters bank hardly ever
- A bank adhering to minimum of regulations, not so often
- Early bird’s third to be stirred? Not often
- Hardly ever right, a bank
Buddy explains!

The straight part
We know that "on only a few occasions" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case on only a few occasions = rarely.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 RARELY mean?
RARELY adverb- Not occurring at a regular interval; seldom; not often.
- Unusually well; excellently.
- To a rare degree; very.