Is Blue about to renounce? (6)
I believe the answer is:
disown
'renounce?' is the definition.
(I've seen this in another clue)
'is blue about' is the wordplay.
'blue' becomes 'down' (both can mean sad).
'about' means one lot of letters goes inside another.
'is' inserted inside 'down' is 'DISOWN'.
'to' is the link.
(Other definitions for disown that I've seen before include "Abnegate" , "Reject all connection with, refuse to acknowledge" , "Wins do (anag)" , "Cast aside" , "Deny any connection with" .)