Sort of reaction produced by commercial poetry (7)
I believe the answer is:
adverse
'sort of reaction produced' is the definition.
I can't judge whether this definition defines the answer.
'by commercial poetry' is the wordplay.
'by' is a charade indicator (letters next to each other).
'commercial' becomes 'ad' (abbreviation for advertisement).
'poetry' becomes 'verse' (lines written in verse).
'ad' next to 'verse' is 'ADVERSE'.
Can you help me to learn more?
(Other definitions for adverse that I've seen before include "Opposed - inauspicious - opposite" , "Inopportune" , "negative result" , "Unfavourable of the week" , "Unfavourable - red vase (anag)" .)