Youngster to switch positions over in place for drill (3,3)
I believe the answer is:
oil rig
'place for drill' is the definition.
(site from which a drill extracts oil)
'youngster to switch positions over' is the wordplay.
'youngster' becomes 'girl'.
'to switch positions' becomes 'io' (as in I and O written on an electronic switch).
'over' says the letters should be written backwards.
'girl'+'io'='girlio'
'girlio' backwards is 'OIL-RIG'.
'in' is the link.
(Other definitions for oil rig that I've seen before include "It's used for drilling, at sea perhaps" , "Structure for drilling for viscous liquid" , "Drilling edifice" , "source of offshore wealth" , "'Structure for drilling (3,3)'" .)