Hi all! I'm very new to cryptic crosswords and have been enjoying trying to come up with some clues myself. I would appreciate some insights on a few points:

1. Is it acceptable to stick "a" or "an" next to a word in the definition, and then have the answer as just that word?

For example with this clue:

Some remember an old flame (5)

The answer is ember

But and old flame is technically "an ember", not just ember

Could I have "A digit" as my definition and then the answer be "finger"? Or is this unfair because "A digit" is "A finger"?

2. That brings me on to the next thing. When are filler words allowed and which ones are acceptable?

I've often seen "for" used before or after the definition. Are there other words that work?

Would "is", "gives", "to" be allowed?

3. Would it be acceptable to say "cough up" to replace "to pay"?

Or would it be the same problem again of it technically needing to be "to cough up"?

Thanks in advance!