The most common and most likely answer to this crossword clue is the 6 letter word ACCESS
I've seen this crossword clue in The Daily Telegraph
A
C
C
E
S
S
More clues leading to the result ACCESS
- Admission, in case dodgy Conservative succeeded
- Idiot guards Catholic church entrance
- Admission of a tax cut by Conservative
- Experts succeeded to introduce constant approach
- Admission of masters degrees ultimately filled out by college
- Admission of cocaine being hidden in a variety of cases
- Gateway for large number to get aboard wonderful ship
- One’s hiding key by south entrance
- Entrance, one admitting first of crew on ship
- Admission made by one catching cold on steamship
Buddy explains!

The straight part
We know that "entrance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case entrance = access.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 ACCESS mean?
ACCESS noun- A way or means of approaching or entering; an entrance; a passage.
- The act of approaching or entering; an advance.
- The right or ability of approaching or entering; admittance; admission; accessibility.
- The quality of being easy to approach or enter.
- Admission to sexual intercourse.
- An increase by addition; accession
- An onset, attack, or fit of disease; an ague fit.
- An outburst of an emotion; a paroxysm; a fit of passion
- The right of a noncustodial parent to visit their child.
- The process of locating data in memory.
- Connection to or communication with a computer program or to the Internet.