The unclued lights (two of two words) are of a kind, verifiable in Brewer.

Across

4 High-handed relation in discussion first (11)
11 This amphibian would need Marvel to make vanilla ice cream (9)
12 Auxiliary doctor taking pulse (5)
14 Ancient Glaswegian notice covering centre of Mull (4)
15/38 Office facility managed 25C (6, two components)
19 Nothing wrong, honest – it’s just a unique attempt (7, hyphened)
22 Suddenly books one Routemaster, say, back (6)
23 Small house and comfy home.