Clue: Claret drunk somewhere in Surrey, where the dormouse's sisters lived (7,4)
Answer: TREACLE WELL
Explanation: Definition: where the dormouse's sisters lived
A charade of TREACL, an anagram ('drunk') of 'claret' plus EWELL ('somewhere in Surrey'). The reference is to *Alice in Wonderland, *and the dormouse's tale of three girls, probably sisters to each other, not the dormouse.