Arran Watt, 22, was handed the tool, which was grabbed by Beverley Meyer outside Hampden Park on August 17 this year.
The Perth club’s supporters liaison officer was pushed to the ground by two unknown men who grabbed the drum from her hands.
The incident sparked a crowd clash with the Union Bears Ranger ultragroup and the police.
Watt struggled with the officers and tried to get away.
He also refused to hand over his personal details until told to do so.
Watt pleaded guilty today at Glasgow Sheriff Court to charges of reset and breaching public order.
He also admitted having a baton without reasonable excuse or lawful authority while on bail for the earlier matters.
The court heard Miss Meyer was working at the time and was in possession of a drum belonging to St Johnstone fans.
Prosecutor Victoria Keel said: “Before the match started she was attacked by two unknown Rangers supporters.
“She was pushed to the ground and the drum violently wrenched from her grasp.
“The men ran back to the Rangers fans who had the drum.”
The hearing heard that the men were being chased by police.
Miss Keel added: “A disorderly crowd then formed as members of the Union Bears tried to protect the men and became aggressive towards the officers.
“Watt, who witnessed the robbery, ran through the crowd and seized the drum, which was handed to him by one of the men.”
Watt was stopped by the police, but he fought them off in an attempt to get away.
At first he refused to give his details until he was forced to do so.
Watt was remanded in custody and released on bail under special conditions.
The hearing was told that Watt was caught with a baton in the driver’s door compartment when he was behind the wheel of an Audi A3 car in the city’s Parkhead on September 1.
Watt was with three other men in the bike that was stopped by police.
Ian Moir, defending, will make his mitigation plea at sentencing next month.
Sheriff Louise Arroll KC said she would consider a football banning order and asked for background reports.
Meanwhile, his remand Watt was continued.