Formation of timeless dark matter, eg on new area of productive land (6,6)
I believe the answer is:
market garden
'area of productive land' is the definition.
(piece of land producing food)
'formation of timeless dark matter eg on new' is the wordplay.
I cannot quite understand how this works, but
'matter' could be 'ga' (Ga is an example) and 'ga' is located in the answer.
'new' could be 'n' (common abbreviation eg NT for New Testament) and 'n' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for market garden that I've seen before include "Small business selling vegetables" , "Place commercially growing fruit and veg" , "Growing concern" , "where food is grown" , "Fruit and veg centre" .)