Don't stop nursing what athlete's overstretched?
I believe the answer is:
tendon
'don't stop nursing' is the definition.
The definition suggests a singular noun which matches the answer.
'what athlete's overstretched?' is the wordplay.
I cannot quite see how this works, but
'athlete' could be 'end' (end is a kind of athlete) and 'end' is present in the answer.
The remaining letters 'ton' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tendon that I've seen before include "Strong cord of tissue connecting muscle" , "Link between bone and muscle" , "Fibrous band" , "Muscle-bone link" , "Strong tissue cord connecting muscles" .)