Fertilizer (7)
I believe the answer is:
nitrate
'fertilizer' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nitrate that I've seen before include "Fertilizer" , "following 28 [SILVER]" , "Fertiliser chemical" , "Tear tin up for fertiliser" , "Nattier (anag.)" .)