### Clue: Wife's exposed buxom rival with no heart (7)
### Answer: UXORIAL 
 ### Explanation: Definition: Wife's
A charade of UXO, '[b]uxo[m]' minus its outer letters ('exposed') plus RIAL, 'ri[v]al' minus it middle letter ('with no heart'). Note that the apostrophe s is part of the definition.