By losing energy, where poor driver may end up (7)
I believe the answer is:
through
'by' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for through that I've seen before include "From one end or side to the other" , "having arrived at next stage" , "By way of - exhausted" , "By means of; having finished a relationship" , "done" .)