Just a few left, which I have kind of worked out but can't derive exactly.
14 across: It's extracted from palm in farming communes(4) _I_I. I think the answer is VICI
20 across: A conspirator punished by post-mortem beheading, not by stocks (6) ACA _ _S. ACARUS?
9 down: Imported horses, second pair bringing up rear, compete at Braemar? (6) _A_S_ _
22 down: Bottled Grolsch - gallons disposed of - in fine (English style) stein (6) S_H_R_
26 down: Nothing occupying a seat that is rertained by a fastener (5) _IPIN
I think Jo already answered that in her second post - 'stein' being the German word for what in the English style would be 'stone', so the definition is 'fine stone'.