Purchase thrown into cart (8)
I believe the answer is:
traction
'purchase' is the definition.
(as in grip on a surface)
'thrown into cart' is the wordplay.
'thrown' indicates anagramming the letters.
'into'+'cart'='intocart'
'intocart' is an anagram of 'TRACTION'.
(Other definitions for traction that I've seen before include "Gripping power to permit movement" , "Act of pulling" , "Pulling power" , "Stretching of a broken bone by weights and pulleys" , "Medical stretching" .)