American orchestra too? (4)
I believe the answer is:
also
'too?' is the definition.
(synonyms)
'american orchestra' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'orchestra' becomes 'LSO' (London Symphony Orchestra).
'a'+'lso'='ALSO'
(Other definitions for also that I've seen before include "item's rarely used now for this" , "'Besides, moreover (4)'" , "Old" , "To boot" , "Item" .)