Clue: Aquatic insect in river starts to nudge drifting reeds around fish (4,6)
Answer: POND SKATER
Explanation: Definition: Aquatic insect
A charade of PO (Italian 'river') plus NDSKATER, an envelope ('around') of SKATE ('fish') in NDR ('starts to **N**udge **D**rifting **R**eeds'). I spent a while trying to fit SPIDER into the second word.