One’s missing having been east on tour (8)
I believe the answer is:
absentee
'one's missing' is the definition.
'been east on tour' is the wordplay.
'on tour' is an anagram indicator (letters tour or travel around).
'been'+'east'='beeneast'
'beeneast' anagrammed gives 'ABSENTEE'.
'having' is the link.
(Other definitions for absentee that I've seen before include "One away from work, etc" , "One who should be but isn't present" , "one's failed to show up" , "shirker?" , "Deserter - truant b" .)