Possible Clues:

• Smell, starting with fish...
• Take off the top and you get the stink of fish
• For strong unpleasant smell point at fish
• Bad aroma
• Dire pong from small fish
• Hum a number in school
• Awful pong
• Fetor
• At last the fish gets up your nose - it's nasty (6)
• Odour of nets suspended over church