Marked by friendliness (8)
I believe the answer is:
sociable
'marked by friendliness' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sociable that I've seen before include "Companionable, friendly" , "Marked by friendliness" , "Friendly - gregarious" , "Easy in company" , "Fond of others' company" .)