Wiktionary
vb. (context transitive English) To give something to a responsible person.
Usage examples of "hand in".
They outnumbered him by four to three, and he'd abandoned any thought of tactical sleight of hand in the face of their steadiness, but he was confident in his ships' qualitative superiority.
He might have reformed considerably since his first tour on Basilisk Station with Tremaine and Lady Harrington, and he'd certainly abandoned the various contraband operations he'd maintained on the side, but a man liked to keep his hand in.
At the end of a long road was a drive that led to a large house, and we stumbled up the darkness of the drive that night, each one of us afraid, each one holding a stone in his hand in case, and all of us too brave to say a word.
Shirley waved a hand in the direction of the hammering coming from outside the south side of the building.
The feel of hardening came stealing through him, and it was as though someone had taken his hand in return.
While you start your analysis of what happened, I'm going to be looking at every single human being who had a hand in the construction.
A friend of mine, who lives at Kingston, went in there to buy a hat one day, and, in a thoughtless moment, put his hand in his pocket and paid for it then and there.