The Rangers midfielder was allowed to find first-team football this season after finding himself down the pecking order thanks to the signings of Glen Kamara and Steven Davis in January and the arrival of Joe Aribo this summer.
The Record are also reporting that Portsmouth will have the option to buy the player when the loan deal expires next summer.
The League One side managed to hold off a last-minute attempt from Jack Ross and Sunderland to pinch the player from under their noses.
McCrorie, who can operate at defensive midfield or centre-back, has played 53 times for the Light Blues after being handed his debut by former boss Pedro Caixinha.
The future transfer fee agreed as part of the loan deal is yet unknown. The value could well have a significant role in whether McCrorie returns to the club next summer.