Possible Clues:

• Fish from lock, we hear
• Cousin of a carp
• Conservative, left of centre -- what's the catch?
• A freshwater fish
• See that the middle of the wheel makes it so fishy
• Carp kin
• Dropping by, plump for fish
• The fish, by the by, is quite fleshy
• River fish; rhymes with public house
• Black porgy, e.g.