Possible Clues:

• A plain standard
• Spear fishes beside Welsh river
• Man after fish with handle of weapon
• Pole for an old infantry weapon (often said to be plain)
• Crew after fish — is that plain?
• Fish workers' means of effecting a run-through
• Take fish with rod, it’s plain
• One of those from school workforce gets some of the stick
• Fish first seen at river, that's plain
• Man chasing fish displaying weapon