A cold needs not to spread - get a tissue (8,6)
'a tissue' is the definition.
(achilles tendon is a kind of tissue)
'a cold needs not to spread' is the wordplay.
'cold' becomes 'chill' (chill is a kind of cold**).
'to spread' indicates an anagram.
'needsnot' is an anagram of 'estendon'.
'get' acts as a link.
(Other definitions for achilles tendon that I've seen before include "part of body", "Tissue", "part of leg", "accident spot", "sinew".)