Fashion on sale as at certain periods (8)
I believe the answer is:
seasonal
'at certain periods' is the definition.
I can't tell whether this defines the answer.
'fashion on sale as' is the wordplay.
'fashion' is an anagram indicator.
'on'+'sale'+'as'='onsaleas'
'onsaleas' is an anagram of 'SEASONAL'.
Can you help me to learn more?
(Other definitions for seasonal that I've seen before include "Relating to spring, summer etc." , "Occurring at particular times of the year" , "Varying according to time of year" , "Also sane (anag.)" , "not wanted all year" .)