Take a breather before the finish line then thrust forward (5)
I believe the answer is:
lunge
'thrust forward' is the definition.
(I've seen this in another clue)
'take a breather before the finish line' is the wordplay.
I cannot really see how this works, but
'breather' could be 'lung' (you breathe with your lungs) and 'lung' is found within the answer.
'before' could be 'e' (I've seen this in other clues) and 'e' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'then' acts as a link.
Can you help me to learn more?
(Other definitions for lunge that I've seen before include "dive" , "Move suddenly" , "Thrust forward as in fencing" , "Thrust, sudden pass" , "Sudden forward movement" .)