### Clue: Third person by eighth vehicle? It may be fruitful (10,4)
### Answer: GOOSEBERRY BUSH 
 ### Explanation: Definition: I
A charade of GOOSEBERRY ('third person' unwanted by an amorous couple) plus BUS H ('eighth vehicle' BUS A etc.), with a definition which may be taken literally, or in the sense of a baby"found under the gooseberry bush".