Aryan rule overthrown in roughly 354 days (5,4)
I believe the answer is:
lunar year
'roughly 354 days' is the definition.
I can't tell whether this defines the answer.
'aryan rule overthrown' is the wordplay.
'overthrown' is an anagram indicator.
'aryan'+'rule'='aryanrule'
'aryanrule' is an anagram of 'LUNAR YEAR'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for lunar year that I've seen before include "some time on the moon" , "Period of twelve new moons" , "Period of 354.3671 days" , "Period of about 354 days" , "Approximately 354 days" .)