Prevent oxidisation with art works in iron (9)
I believe the answer is:
frustrate
'prevent' is the definition.
(frustrating is a kind of preventing)
'oxidisation with art works in iron' is the wordplay.
'oxidisation' becomes 'rust' (rust is a kind of oxidisation**).
'with' says to put letters next to each other.
'works' is an anagram indicator.
'in' indicates putting letters inside.
'iron' becomes 'fe' (Fe is the chemical symbol for iron).
'art' anagrammed gives 'rat'.
'rust'+'rat'='rustrat'
'rustrat' inserted within 'fe' is 'FRUSTRATE'.
(Other definitions for frustrate that I've seen before include "Prevent from progressing" , "'Thwart, disappoint (9)'" , "Put a stop to" , "Prevent (plan) from being fulfilled" , "Deprive of hope" .)