Kranjcar, who left Spurs for Dynamo Kiev in 2012, has been signed by Redknapp for a third time having also played for him at Portsmouth.
Redknapp commented: "Niko's a crowd pleaser - he gets people off their seats.
"He's a top player and someone who will add great quality to the squad.
"He's someone I obviously know a lot about and he'll be a fantastic addition for us."
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