Skiver ecstatic, a worker claims (8)
I believe the answer is:
absentee
'skiver' is the definition.
(I've seen this before)
'ecstatic a worker claims' is the wordplay.
'ecstatic' becomes 'sent' (I've seen this in other clues).
'worker' becomes 'bee' (I've seen this before).
'claims' means one lot of letters goes inside another.
'a'+'bee'='abee'
'sent' put inside 'abee' is 'ABSENTEE'.
(Other definitions for absentee that I've seen before include "Missing person" , "One away from work, etc" , "one's failed to show up" , "One who stays away" , "to prompt a hearty increase in affection!" .)