Emblem of country's peerage lads vandalised (6,5)
I believe the answer is:
spread eagle
'emblem of country's' is the definition.
(emblem of the United States)
'peerage lads vandalised' is the wordplay.
'vandalised' is an anagram indicator.
'peerage'+'lads'='peeragelads'
'peeragelads' anagrammed gives 'SPREAD-EAGLE'.
(Other definitions for spread eagle that I've seen before include "Stretch out with arms and legs extended" , "Skating figure" , "Symbol of powerful nation" , "US emblem" , "Stretch (someone) out with limbs extended" .)