Point on back of dry riser? (5)
I believe the answer is:
yeast
'riser?' is the definition.
(I've seen this in another clue)
'point on back of dry' is the wordplay.
'point' becomes 'east' (east is a kind of point).
'on' is a charade indicator (letters next to each other).
'back of' says to take the final letters.
The last letter of 'dry' is 'y'.
'east' put after 'y' is 'YEAST'.
(Other definitions for yeast that I've seen before include "Fungus; food supplement" , "Agent for making bread" , "Dough raising agent" , "Fungus used in brewing and baking" , "Organism causing fermentation" .)