Fish in quiet river with mischievous child (6)
I believe the answer is:
shrimp
'fish' is the definition.
(shrimping is a kind of fishing)
'quiet river with mischievous child' is the wordplay.
'quiet' becomes 'sh'.
'river' becomes 'r'.
'with' is a charade indicator (letters next to each other).
'mischievous child' becomes 'imp' (I've seen this before).
'sh'+'r'+'imp'='SHRIMP'
'in' is the link.
(Other definitions for shrimp that I've seen before include "tiny chap" , "Runt" , "Small, weak person" , "Tasty crustacean found in cocktails" , "colour?" .)