Order to work out (5)
I believe the answer is:
train
I believe this is a double definition.
'order' is the first definition.
(train is a kind of order)
'work out' is the second definition.
(training is a kind of working out)
'to' acts as a link.
(Other definitions for train that I've seen before include "Railway engine" , "School, educate" , "Public transport on the railway" , "held up in union action?" , "Line of carriages with a locomotive" .)