Clue: Rejected new street map that's variable and eccentric (4)
Answer: ZANY
Explanation: Definition: eccentric
 **Reversal of**(Rejected) [ N(abbrev. for "new") + AZ("A-Z", any of a range of street maps of a particular area published by the Geographers' A–Z Map Company, UK) ] **plus**(that's) Y(symbol for a variable quantity in mathematics).