Related Clues:

• Not transparent, light can't pass through
• Dull, overcast
• Not clear or transparent
• Cloudy, not transparent
• Overcast, nebulous
• 'Overcast, nebulous (6)'
• It's not clear how noisey this can get during December, in short
• It's a bit thick to get round Father at the head of the queue
• It's a bit thick to give work such a queer start
• It's a bit thick to get around to Father at the head of the queue
• It's 10 across with lots in it, by the sound of it
• Through anything like this it's unseen
• There's a lot, by the sound of it, obscured during December back here
• A bit thick, O Dad, to start 17 across this way
• In chess, when to swop a queen isn't clear