1: Damn turncoat left country (9)
2: Actor works on two dialects (5,8)
3: Navigate by terse directions (5)
4: Savings division of e-banking gets enormous returns (4,3)
5: Tar mess contaminated rivers (7)
6: Waste pores vent exhausted resources (9)
7: Its strange to go back to a novice for a wall decoration (5)
10: Repeated note to help player? (6-7)
13: Page keeps lighting fires in church building (9)
15: Consigned elegant, short, new dresses in red (9)
17: Hang around and look at that old Roman road (6)
18: Fathers admitting a couple of atrocious spoofs (7)
20: Strap, though short, has hanger's heart (5)
21: Its difficult to include the overhead in the cache (5)