One who's sponsored idol given stick crossing line (8)
I believe the answer is:
godchild
'one who's sponsored' is the definition.
(sponsor can mean a godparent)
'idol given stick crossing line' is the wordplay.
'idol' becomes 'god' (synonyms).
'given stick' becomes 'chid' (past tense of chide - to criticise or give stick).
'crossing' means one lot of letters goes inside another.
'line' becomes 'l'.
'chid' enclosing 'l' is 'child'.
'god'+'child'='GODCHILD'
(Other definitions for godchild that I've seen before include "Sponsored individual" , "Sponsored baptised baby" , "Person to whom one made promises at baptism" , "Religious protege" , "Sponsored youngster" .)