Endurance, so to speak (4)
I believe the answer is:
legs
'endurance so to speak' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for legs that I've seen before include "associated with 11 in game" , "Lower limbs" , "Members" , "Stages of a journey" , "Sections of a journey or course" .)