### Clue: Former duck trap that is snaring mallard's head (7)
### Answer: ONETIME 
 ### Explanation: Definition: Former
 O(letter representing 0;a duck in cricket, signifying 0 runs scored) + NET(a trap to ensnare something or someone) + IE(abbrev. for the Latin "id est";that is) **containing**(snaring) **1st letter of**(…'s head) "mallard".