Record hosts fail to keep to (6)
I believe the answer is:
closed
'to' is the definition.
(I've seen this before)
'record hosts fail to keep' is the wordplay.
'record' becomes 'cd' (I've seen this in other clues).
'hosts' means one lot of letters goes inside another.
'fail to keep' becomes 'lose' ('lose' can be a synonym of 'fail to keep').
'cd' placed around 'lose' is 'CLOSED'.
(Other definitions for closed that I've seen before include "See 1" , "Concluded or fastened" , "Blocked off" , "Held in private" , "restricted" .)