English set back by one article in periodical (7)
I believe the answer is:
etesian
'periodical' is the definition.
Both the definition and answer are adjectives.
Maybe there's an association between them I don't understand?
'english set back by one article' is the wordplay.
'english' becomes 'E' (abbreviation).
'back' is a reversal indicator.
'by' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'article' becomes 'an' (English indefinite article).
'set' in reverse letter order is 'tes'.
'e'+'tes'+'i'+'an'='ETESIAN'
'in' is the link.
Can you help me to learn more?
(Other definitions for etesian that I've seen before include "returning every year" , "(Of winds) blowing each summer; sea nite (anag.)" , "Periodical (as some winds and wells)" , "(Of certain winds) seasonal; tease in (anag.)" .)