Bit of broken stuff in river swallowed by fish (5)
I believe the answer is:
shard
'bit of broken stuff' is the definition.
'shard' can be an answer for 'bit' (I have seen 'Bit of glass' mean 'shard' so perhaps 'bit' could also mean 'shard'). I am not sure about the 'of broken stuff' bit.
'river swallowed by fish' is the wordplay.
'river' becomes 'r' (abbreviation for river).
'swallowed by' is an insertion indicator.
'fish' becomes 'shad' (shad is a kind of fish).
'r' put into 'shad' is 'SHARD'.
'in' is the link.
Can you help me to learn more?
(Other definitions for shard that I've seen before include "archaeological find" , "Sliver of glass, etc" , "remnant after break-up" , "Broken piece of a brittle artefact" , "Broken bit" .)