Too advanced group of musicians (4)

I believe the answer is:

also

'too' is the definition.
(synonyms)

'advanced group of musicians' is the wordplay.
'advanced' becomes 'a'.
'group of musicians' becomes 'LSO' (London Symphony Orchestra).
'a'+'lso'='ALSO'

(Other definitions for also that I've seen before include "in accompaniment" , "revolutionary a part for Yugoslavia" , "As well, in addition" , "on top" , "Plus" .)

I've seen this clue in The Telegraph.

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