Rubbish surface turned into something suitable for lawn (7)
I believe the answer is:
aerator
'something suitable for lawn' is the definition.
'rubbish surface turned' is the wordplay.
'rubbish' becomes 'rot' (both can mean nonsense).
'surface' becomes 'area' (I've seen this in another clue).
'turned' shows that the letters should be reversed in order.
'rot'+'area'='rotarea'
'rotarea' backwards is 'AERATOR'.
'into' acts as a link.
(Other definitions for aerator that I've seen before include "One may emit much gas" , "Tropical fish tank pump" , "Device introducing air" , "Maybe fork" , "Device such as used in tropical fish tanks" .)