Collect in a truck (4,2)
I believe the answer is:
pick up
This clue is a double definition.
'collect' is the first definition.
(I know that collect can be written as pick up)
'truck' is the second definition.
(pick-up is a kind of truck)
'in a' acts as a link.
(Other definitions for pick up that I've seen before include "Acquire by chance" , "lift" , "vehicle" , "Collect - improve - learn" , "van when the economy is > improving" .)