Clues are presented in strict alphabetical order of their solutions. Solvers have to assign the solutions to their correct places in the grid jigsaw-fashion.
 
A) A French messenger’s unending rage (4)
Unaltered first principle that’s non-British (4, two words)
Far off (4)
 
B)  Litter from Mark outside vehicle (8)
 
C)  Sinclair gets off at Norfolk keep (12, two words)
Confirm listed items, we’re told, for dramatist (7)
 
D)  Last old leading Renaissance artist (5)
 
E)  Awfully hot aldermen absorbing heat (11)
 
F)  Hunts since heavens knows when (7)
 
G)  One sitting by the roadside, it’s said, in latex (11, hyphened)
 
H)  Greets former Tory lord, not one who overacts (5)
Some posh, if...