Related Clues:

• Investigated as dentist does tooth
• Investigated closely as dentist does a tooth
• "Because seven ___ nine" (punchline)
• Questioned or examined thoroughly and closely
• Investigating closely
• Little more than one of 9 across, by the sound of it
• If after half a century this had one dead, it was something one swallowed
• One must be candid with this if one wants the job
• Four and four - that's what you took to be so sound
• What a filly did, by the sound of it, to join up
• It's not what you did this that has you one over it, by the sound of it
• If in fur I did this, it would make you very warm
• Little more than 29 across, by the sound of it
• S, even one more, by the sound of it
• What Noah never did with 18 down