* Aids
* Aisle
* Ajar
* Amok
* Ante
* Apex
* Arms
* Arts
* Asks
* Axis
* Abet
* Abed
* Abey
* Able
* Ably
* Abse
* Abut
* Ache
* Acts
* Adieu
* Adit
* Adze
* Afar
* Afoot
* Again
* Agha
* Agon
* Ahoy
* Aids
* Aisle
* Ajar
* Amok
* Ante
* Apex
* Arms
* Arts
* Asks
* Axis
This is not an exhaustive list, and there may be more 4-letter words starting with "a".