Providing the spymaster with cues for clues in Codenames
It does not address this directly in the rules but based on my reading it is illegal and against the spirit of the game. The game is wanting you to convey information from the spymaster to the operatives with a single word. While it may be acceptable to take the deliberations that the operatives have after a clue is given into account having them give directions on what to say is different.

If you look at the Keeping A Straight Face section of the rules it goes into the intent behind how clues are given.


  The spymaster is expected to keep a straight
  face. Do not reach for any card while your
  teammates are considering the words. When
  a teammate touches a word, consult the key
  card and cover the word with the card of
  the corresponding color. When a teammate
  chooses a word of the correct color, you
  should act as though it was exactly the word
  you meant, even if it wasn't.  
  
  If you are a field operative, you should focus
  on the table when you are making your
  guesses. Do not make eye contact with the
  spymaster while you are guessing. This will
  help you avoid nonverbal cues.    
  
  When your information is strictly limited to
  what can be conveyed with one word and one
  number, you are playing in the spirit of the game.