Rest day ruined by having got lost (7)
I believe the answer is:
strayed
'lost' is the definition.
(thesaurus)
'rest day ruined' is the wordplay.
'ruined' indicates anagramming the letters.
'rest'+'day'='restday'
'restday' anagrammed gives 'STRAYED'.
'by having got' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for strayed that I've seen before include "Erred, wandered" , "Went off course" , "Dry seat (anag) - got lost" , "Went wrong" , "Went off the track" .)