Vitamin helping blood to clot stops skin peeling (5)
I believe the answer is:
flaky
'peeling' is the definition.
(flaking off)
'vitamin helping blood to clot stops skin' is the wordplay.
'vitamin helping blood to clot' becomes 'K' (Vitamin K).
'stops' indicates putting letters inside.
'skin' becomes 'flay' (flay can mean to take something's skin off).
'k' inserted inside 'flay' is 'FLAKY'.
(Other definitions for flaky that I've seen before include "Easily separating; unreliable" , "Tending to break or peel off - crazy" , "pastry" .)