Spear with identification found in the river (7)
I believe the answer is:
trident
'spear' is the definition.
(trident is a kind of spear)
'identification found in the river' is the wordplay.
'identification' becomes 'id'.
'found in' is an insertion indicator.
'the river' becomes 'trent' (I've seen this before**).
'id' put into 'trent' is 'TRIDENT'.
'with' acts as a link.
(Other definitions for trident that I've seen before include "Submarine missile" , "spear carried at sea" , "Neptune's weapon" , "Spear held by Neptune or Britannia" , "A three-pronged spear as wielded by Neptune" .)