It helps to raise poet as son moves back (5)
I believe the answer is:
yeast
'moves back' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'it helps to raise poet as son' is the wordplay.
I cannot really understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
'as' is found in the answer.
The remaining letters 'ye' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for yeast that I've seen before include "It makes dough rise" , "Organism causing fermentation" , "Bread-making component" , "Fungus used in fermenting" , "Brewer's agent" .)