Weekly letter to a wandering nomad (6)
I believe the answer is:
monday
'weekly' is the definition.
(weekly occurrence)
'letter to a wandering nomad' is the wordplay.
'letter' becomes 'y' (Y is a letter of the alphabet).
'to' says to put letters next to each other (I've seen this in other clues).
'a wandering' indicates anagramming the letters.
'nomad' with letters rearranged gives 'monda'.
'y' after 'monda' is 'MONDAY'.
(Other definitions for monday that I've seen before include "Dynamo (anag.)" , "First weekday" , "Part of the week" , "Week day" , "May nod (anag.)" .)