Spike is heard from river (4)
I believe the answer is:
tyne
'river' is the definition.
(I've seen this before)
'spike is heard' is the wordplay.
'spike' becomes 'tine' (spike of a fork).
'is heard' indicates a 'sounds like' (homophone) clue.
'tine' sounds like 'TYNE'.
'from' is the link.
(Other definitions for tyne that I've seen before include "Banker" , "North of England river" , "Serve as evidence for" , "Northumbrian river" , "River at Gateshead" .)