Possible Clues:

• Tricky thing to trisect, in classical geometry
• Matter of degree?
• Fish — tons coming out from seaweed
• Fish deviously obtained is topped and tailed
• Way of looking at things
• Fish nibbling top off seaweed
• It may be acute or right
• Billiards shot concern
• It's all a matter of degree
• Drop a line from a pier, say