Fantastic offer Hector ultimately declined is not to be made public (3,3,6)
I believe the answer is:
off the record
'not to be made public' is the definition.
(I've seen this before)
'fantastic offer hector ultimately declined' is the wordplay.
'fantastic' indicates anagramming the letters.
'ultimately' says to take the final letters.
The final letter of 'declined' is 'd'.
'offer'+'hector'='offerhector'
'offerhector' anagrammed gives 'offtherecor'.
'offtherecor'+'d'='OFF-THE-RECORD'
'is' acts as a link.
(Other definitions for off the record that I've seen before include "not publicly aired" , "unprintable" , "Deleted from disc" , "Sub rosa" , "Unofficially" .)