Close friends, to some extent (3)
I believe the answer is:
end
'close' is the definition.
(close can mean to end or finish)
'friends to some extent' is the wordplay.
'to some extent' indicates a hidden word.
'END' is hidden within 'friends'.
(Other definitions for end that I've seen before include "Termination" , "death" , "Purpose of finish" , "Aim; terminate" , "border?" .)