A sturdy husband strays once a week it appears (8)
I believe the answer is:
thursday
'once a week it appears' is the definition.
(Thursday happens once a week)
'a sturdy husband strays' is the wordplay.
'husband' becomes 'h'.
'strays' is an anagram indicator.
'a'+'sturdy'+'h'='asturdyh'
'asturdyh' is an anagram of 'THURSDAY'.
(Other definitions for thursday that I've seen before include "Chesterton's man" , "Thunder god's period" , "twenty-four hours" , "Day of the week" , "Rash duty (anag)" .)