Lock up one acquiring work experience (6)
I believe the answer is:
intern
'lock up' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for intern that I've seen before include "Confine the hospital resident" , "Confine to camp" , "Confine - assistant medic in America" , "Confine the hospital doctor" , "put in jail" .)