Wandered off, wasting rest day (7)
I believe the answer is:
strayed
'wandered off' is the definition.
(I've seen this in another clue)
'wasting rest day' is the wordplay.
'wasting' is an anagram indicator (waste can mean to destroy).
'rest'+'day'='restday'
'restday' with letters rearranged gives 'STRAYED'.
(Other definitions for strayed that I've seen before include "Wandered away" , "Dry seat (anag) - got lost" , "Erred, wandered" , "Wandered (from path)" , "Went off the track" .)