### Clue: Towers of hams on a pair of trays (8)
### Answer: TRACTORS 
 ### Explanation: Definition: Towers
  ACTORS(who overact are "hams") **placed after**(on, in an across clue) **the 1st two letters of**(a pair of) "trays ". 
Defn:  Tow-ers, eg. used to tow farming equipment.