### Clue: Author not available to support small firm over summons (8)
### Answer: SUBPOENA 
 ### Explanation: Definition: summons
 [ POE(Edgar Allan, American author) + N.A.(abbrev. for "not available"] **placed below**(to support, in a down clue) **reversal of**(… over, in a down clue) BUS(short for;small "business";a commercial firm).