Bring down on the gridiron (6)
I believe the answer is:
tackle
'bring down on the gridiron' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tackle that I've seen before include "Come to grips with the fishing equipment" , "Try - made by a rugby player?" , "A rugby interception" , "man's genitals" , "Start dealing with the fishing equipment" .)