labonadom,
A caution is a police record not a conviction, so if you are asked if you have a conviction you can quite rightly answer no.
However the caution stays on file with the police for as long as that force keeps thier records.
In this computer age, this can now mean forever.
In applying for your licence to be a publican the caution will more than likely show in an enhanced disclosure.
It is a matter for yourself if you do or don;t disclose it but more and more employers are allowing minor spent cautions and convictions to be discounted.
They may consider you to be totally honest if you do disclose this caution and hold you in greater favour.
If you were cautioned at 17 or under the caution will not show on a CRB as you were not an adult.
BEST OF LUCK