Fearing rust, a form of change (11)
I believe the answer is:
transfigure
'change' is the definition.
(I've seen this before)
'fearing rust a form' is the wordplay.
'a form' indicates an anagram (a different form of the same letters).
'fearing'+'rust'='fearingrust'
'fearingrust' is an anagram of 'TRANSFIGURE'.
'of' acts as a link.
(Other definitions for transfigure that I've seen before include "Make (something) more spiritual" , "Change into something more beautiful or spiritual" .)