37a (not 17a?) Roux infused with bay leaves and clove-studded onions, used in dishes such as cauliflower cheese, croque monsieur, lasagane and moussaka (8,5)
13d Sir Gawain and the Green -------. one of the legendary Arthurian tales (6)
19d Chemical element used in electronic circuits, atomic No 14 (7)
40d Biologist who studies the interrelationships between organisms and their environments (9)
41 Great ---- of Gaza, one of the seven wonders of the ancient world (7)
53d General term for an expanse where 'white horses' may be observed (3)