Nothing brought up by king to make connection (4)
I believe the answer is:
link
'connection' is the definition.
(I know that connection can be written as link)
'nothing brought up by king' is the wordplay.
'nothing' becomes 'nil' (eg nil is zero in football).
'brought up' says the letters should be written in reverse (in a down clue, letters go up).
'by' means one lot of letters go next to another.
'king' becomes 'K' (chess abbreviation).
'nil' written backwards gives 'lin'.
'lin'+'k'='LINK'
'to make' is the link.
(Other definitions for link that I've seen before include "Relationship; loop in a chain" , "Connexion" , "Join together" , "One ring or loop of a chain" , "A chain is as strong as its weakest one" .)