Crossword Genius

Spies blocking a single performance mostly unfriendly (7)

Ross

I believe the answer is:

asocial

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'unfriendly' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?

'spies blocking a single performance mostly' is the wordplay.
'spies' becomes 'CIA' (Central Intelligence Agency).
'blocking' is an insertion indicator (to block can mean to plug a gap in something).
'single performance mostly' becomes 'sol' (I can't justify this - if you can you should believe this answer much more).
'a'+'sol'='asol'
'cia' put within 'asol' is 'ASOCIAL'.

Can you help me to learn more?

(Other definitions for asocial that I've seen before include "without friends" , "Inconsiderate to others" , "Not fond of company, perhaps inconsiderate" , "Avoiding company" , "Not gregarious" .)

I've seen this clue in The Times.
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