Sacrifice of old boy left country leaderless (8)
I believe the answer is:
oblation
'sacrifice' is the definition.
(oblation is a sacrifice or offering to a god)
'old boy left country leaderless' is the wordplay.
'old boy' becomes 'OB' (abbreviation for a private school 'old boy').
'left' becomes 'l' (common abbreviation).
'country' becomes 'nation' (synonyms).
'leaderless' means to remove the first letter.
'nation' with its first letter taken away is 'ation'.
'ob'+'l'+'ation'='OBLATION'
'of' acts as a link.
(Other definitions for oblation that I've seen before include "Ritual offering" , "To Albion, with an offering to the divine" , "Part of Eucharist" , "Religious or charitable offering" , "Offering to divinity" .)