Covering with fertilizer (8)
I believe the answer is:
dressing
This clue is a double definition.
'covering' is the first definition.
(dressing is a kind of covering)
'fertilizer' is the second definition.
(thesaurus)
'with' is the link.
(Other definitions for dressing that I've seen before include "Sauce - alignment - bandage" , "bedroom procedure?" , "French or vinaigrette, say" , "Covering for wound; sauce for salad" , "but not stripping!" .)