One possible answer is heaven. (Another is seal.) The words all go with numbers:
- first aid
- second-guess
- third degree
- fourth estate
- Fifth Avenue
- sixth sense
- seventh heaven / seventh seal
You could create other puzzles with the same premise:
- amendment
- hand
- world
- dimension
- wheel
Of course, all of those could be amendment, or the first three of them could be base or degree or estate or world. But in most of the above cases I think the numbers given are the numbers most commonly associated with the given words.
You could also do a silly version of the puzzle:
- yousayyoudoandthenyoudon't
- themotion
- time'sthecharm
- forbridge
- ofwhiskey
But somehow I think it would be easier to guess the answer to that version.