Clue: Drive shown by old boy in Hertfordshire town producing theatrical costumes (8)
Answer: WARDROBE
Explanation: Definition: theatrical costumes
 [ DR(abbrev. for "Drive", as in home addresses) **plus**(shown by) OB(abbrev. for "old boy", formerly from a school or university) ] **contained in**(in) WARE(a town in Hertfordshire, England).