1: Addition of some more flexible thinking (15)
4: Initiate discovered in boffo underwear (5)
6: Vicar regularly outdated technology (1.1.1.)
8: Centre of diamond is shrouded in fog (5)
11: Outfit in which one walks when outside the ship? (9)
12: Pate topping primarily honey and tamari? (3)
13: Native American involved in drug problem exposed (5)
15: Faith in Osiris, lamentably (5)
16: Boy scurries around Alabama parlor (5)
17: Attack set up by funny-looking little green man (5)
19: Sheep to start wallowing in ease (3)
20: Boggy terrain didn't sink Plan C's successor? (9)
23: Sigh audibly about fool giving lip (5)
24: Famous gardens said to move one to speak. (3)
25: More extensive extra, right? (5)
26: Offer one's hand to an accountant by way of an alternative bid. (15)