Eschewing contact with others, start to assess note spies left (7)
I believe the answer is:
asocial
'eschewing contact with others' is the definition.
(someone who doesn't socialise)
'start to assess note spies left' is the wordplay.
'start to' indicates taking the first letters.
'note' becomes 'so' (musical note).
'spies' becomes 'CIA' (Central Intelligence Agency).
'left' becomes 'L' (common abbreviation).
The initial letter of 'assess' is 'a'.
'a'+'so'+'cia'+'l'='ASOCIAL'
(Other definitions for asocial that I've seen before include "not connected with community" , "Avoiding company" , "Solitary" , "Inconsiderate to others" , "cold" .)