There is a total of 21196 clues beginning with si
- Signal from the third base coach, maybe
- Signal from the wings
- Signal giver
- Signal giver
- Signal givers
- Signal hello or goodbye
- Signal hinted at by the first parts of 17-, 31- and 46-Acros
- Signal historical stage
- Signal horns of yore
- Signal in a courtroom
- Signal in bridge
- Signal in Morse code
- Signal in the Gotham City sky
- Signal increaser
- Signal interference
- Signal items
- Signal light
- Signal light on 4/18/'75
- Signal light
- Signal lights of a certain kind
- Signal lights
- Signal like "Mayday"
- Signal made official in 1912
- Signal meaning "help"
- Signal meaning "no disease on this ship"
- Signal of a kind
- Signal of a kind
- Signal of a sort
- Signal of a sort
- Signal of approval
- Signal of comprehension
- Signal of distress
- Signal of distress
- Signal of imminent attack
- Signal of imminent danger
- Signal of insight
- Signal on a radar apparatus
- Signal on a screen
- Signal on stage
- Signal on the hour
- Signal on the road
- Signal one's agreement
- Signal one's consent
- Signal one's parting
- Signal one's punches
- Signal or indicate
- Signal or Marine
- Signal or trooper preceder
- Signal or work starter
- Signal period in history
- Signal period of time
- Signal pick-upper
- Signal quality symbols
- Signal receiver
- Signal receivers
- Signal relayer
- Signal sayonara
- Signal seeking silence
- Signal sender
- Signal sent by Carlsen
- Signal shade
- Signal showing a storm's position
- Signal signals?
- Signal silently
- Signal since 1912
- Signal site of 4/18/'75
- Signal sounded by a bugle
- Signal stage of history
- Signal stages of history
- Signal strengthener
- Signal subtly
- Signal surreptitioulsy
- Signal system
- Signal systems
- Signal that a reply is coming in a messaging app
- Signal that danger has passed
- Signal that ends 50 Across
- Signal that everything's OK
- Signal that had only existed for a few years when the RMS Titanic used it
- Signal that may allay anxiety
- Signal that one's eggs are done?
- Signal that one's ready for dinner?
- Signal that replaced "CQD"
- Signal that starts a scramble
- Signal that the game's over by the Irish ref? (Prince / Living Colour)
- Signal that's a palindrome in English and Morse code
- Signal the auctioneer
- Signal the coming of
- Signal the dawn, in a way
- Signal the doctor
- Signal the end
- Signal the genie
- Signal to a road hog
- Signal to a runner
- Signal to act
- Signal to an actor
- Signal to an on-call doctor
- Signal to begin speaking
- Signal to begin speaking, perhaps
- Signal to begin