A fair way out on Sunday excursion (6)
I believe the answer is:
safari
'excursion' is the definition.
(thesaurus)
'a fair way out on sunday' is the wordplay.
'way out' indicates an anagram.
'on' says to put letters next to each other.
'sunday' becomes 's'.
'fair' is an anagram of 'fari'.
'a'+'fari'='afari'
'afari' put after 's' is 'SAFARI'.
(Other definitions for safari that I've seen before include "North African capital" , "Expedition to observe animals" , "Big game trip" , "Trip to see wild animals" , "Hunting journey" .)