Thus I appear in the telegram to be gregarious (8)
I believe the answer is:
sociable
'be gregarious' is the definition.
(I've seen this before)
'thus i appear in the telegram' is the wordplay.
'thus' becomes 'so' (synonyms).
'appear in' means one lot of letters goes inside another.
'the telegram' becomes 'cable' (cable is a kind of telegram).
'i' going within 'cable' is 'ciable'.
'so'+'ciable'='SOCIABLE'
'to' acts as a link.
(Other definitions for sociable that I've seen before include "Easy in company" , "Fond of mixing with others" , "Friendly and pleasant" , "Fond of others' company" , "Companionable, friendly" .)