Attack commercial support for iron being processed (6)
I believe the answer is:
inroad
'attack' is the definition.
(inroad is a kind of attack)
'commercial support for iron being processed' is the wordplay.
'commercial' becomes 'ad' (abbreviation for advertisement).
'support for' says to put letters next to each other (in a down clue, some letters 'support' others).
'being processed' indicates anagramming the letters.
'iron' with letters rearranged gives 'inro'.
'ad' put after 'inro' is 'INROAD'.
(Other definitions for inroad that I've seen before include "Encroachment; hostile attack" , "Ordain (anag.)" , "Incursion, raid" , "Offensive" , "One's intrusive" .)