To jack something in.
“It’s not even nine months since Johnny Murtagh retired from a riding career that confirmed him one of the greatest jockeys this country has ever produced. … That he jacked it in at 43 was a surprise, but only to an extent, considering the context of a life spent battling weight.” — Irish Times, 3 Nov 2014
According to Wikipedia, “in the British idiom, the object may appear before or after the particle. If the object is a pronoun, then it must be before the particle.”
To give up or chuck something in — like a job, or studies.