1: English philosopher cured pig (5)
2: Talked about an urban area in the NW (7)
3: Unidentified street across the Mountains (7)
4: Illness I catch performing exercises? (13)
5: English scenes reproduced for 'Nature' (7)
6: Almost reveal Nationals' former identity (5)
8: Ships use up aid at sea; remain in a grave situation (4,2,7)
9: Collars rowdies in the audience (5)
11: About....about right? Wrong! (3)
13: Height is equal to three-fifths of the first one (3)
15: Endless barbecue arranged for young carnivore (4,3)
16: Person believing - except for Satanic evil (5)
17: Snob detaining listener? Flee! (4,3)
18: Send inmates free gin (7)
19: Drunk band I conducted (5)
20: Siphon windy painter? (5)