Possible Clues:

• [*cross out* Studio substitute] Squarish bed?
• *Movie stand-in
• Film star's stand-in
• Ryan Gosling's role in "The Fall Guy"
• Stunt stand-in
• Dictator's stand-in, perhaps
• *Actor's stand-in
• *Stand-in on set
• Stand-in during a film shoot ... or a hint to 17-, 25-, 38- and 51-Across
• Performer whose face is rarely seen