Possible Clues:

• Slender fibre
• Thin wire, in a bulb say
• Fine thread
• Fine fibre
• If it starts to sound sad, you may make light of it
• Cable broadcast neat film
• Fibre provided by fine malt whisky?
• It glows if it turns sad, by the sound of it
• Thread-like object
• If raising complaint, one can become incandescent